001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     * 
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     * 
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.lang;
018    
019    import org.apache.commons.lang.math.NumberUtils;
020    
021    /**
022     * <p>Operations on boolean primitives and Boolean objects.</p>
023     *
024     * <p>This class tries to handle <code>null</code> input gracefully.
025     * An exception will not be thrown for a <code>null</code> input.
026     * Each method documents its behaviour in more detail.</p>
027     * 
028     * @author Apache Software Foundation
029     * @author Matthew Hawthorne
030     * @author Gary Gregory
031     * @since 2.0
032     * @version $Id: BooleanUtils.java 905636 2010-02-02 14:03:32Z niallp $
033     */
034    public class BooleanUtils {
035    
036        /**
037         * <p><code>BooleanUtils</code> instances should NOT be constructed in standard programming.
038         * Instead, the class should be used as <code>BooleanUtils.toBooleanObject(true);</code>.</p>
039         *
040         * <p>This constructor is public to permit tools that require a JavaBean instance
041         * to operate.</p>
042         */
043        public BooleanUtils() {
044          super();
045        }
046    
047        // Boolean utilities
048        //--------------------------------------------------------------------------
049        /**
050         * <p>Negates the specified boolean.</p>
051         * 
052         * <p>If <code>null</code> is passed in, <code>null</code> will be returned.</p>
053         *
054         * <pre>
055         *   BooleanUtils.negate(Boolean.TRUE)  = Boolean.FALSE;
056         *   BooleanUtils.negate(Boolean.FALSE) = Boolean.TRUE;
057         *   BooleanUtils.negate(null)          = null;
058         * </pre>
059         * 
060         * @param bool  the Boolean to negate, may be null
061         * @return the negated Boolean, or <code>null</code> if <code>null</code> input
062         */
063        public static Boolean negate(Boolean bool) {
064            if (bool == null) {
065                return null;
066            }
067            return (bool.booleanValue() ? Boolean.FALSE : Boolean.TRUE);
068        }
069        
070        // boolean Boolean methods
071        //-----------------------------------------------------------------------
072        /**
073         * <p>Checks if a <code>Boolean</code> value is <code>true</code>,
074         * handling <code>null</code> by returning <code>false</code>.</p>
075         *
076         * <pre>
077         *   BooleanUtils.isTrue(Boolean.TRUE)  = true
078         *   BooleanUtils.isTrue(Boolean.FALSE) = false
079         *   BooleanUtils.isTrue(null)          = false
080         * </pre>
081         *
082         * @param bool  the boolean to check, null returns <code>false</code>
083         * @return <code>true</code> only if the input is non-null and true
084         * @since 2.1
085         */
086        public static boolean isTrue(Boolean bool) {
087            if (bool == null) {
088                return false;
089            }
090            return bool.booleanValue() ? true : false;
091        }
092    
093        /**
094         * <p>Checks if a <code>Boolean</code> value is <i>not</i> <code>true</code>,
095         * handling <code>null</code> by returning <code>true</code>.</p>
096         *
097         * <pre>
098         *   BooleanUtils.isNotTrue(Boolean.TRUE)  = false
099         *   BooleanUtils.isNotTrue(Boolean.FALSE) = true
100         *   BooleanUtils.isNotTrue(null)          = true
101         * </pre>
102         *
103         * @param bool  the boolean to check, null returns <code>true</code>
104         * @return <code>true</code> if the input is null or false
105         * @since 2.3
106         */
107        public static boolean isNotTrue(Boolean bool) {
108            return !isTrue(bool);
109        }
110    
111        /**
112         * <p>Checks if a <code>Boolean</code> value is <code>false</code>,
113         * handling <code>null</code> by returning <code>false</code>.</p>
114         *
115         * <pre>
116         *   BooleanUtils.isFalse(Boolean.TRUE)  = false
117         *   BooleanUtils.isFalse(Boolean.FALSE) = true
118         *   BooleanUtils.isFalse(null)          = false
119         * </pre>
120         *
121         * @param bool  the boolean to check, null returns <code>false</code>
122         * @return <code>true</code> only if the input is non-null and false
123         * @since 2.1
124         */
125        public static boolean isFalse(Boolean bool) {
126            if (bool == null) {
127                return false;
128            }
129            return bool.booleanValue() ? false : true;
130        }
131    
132        /**
133         * <p>Checks if a <code>Boolean</code> value is <i>not</i> <code>false</code>,
134         * handling <code>null</code> by returning <code>true</code>.</p>
135         *
136         * <pre>
137         *   BooleanUtils.isNotFalse(Boolean.TRUE)  = true
138         *   BooleanUtils.isNotFalse(Boolean.FALSE) = false
139         *   BooleanUtils.isNotFalse(null)          = true
140         * </pre>
141         *
142         * @param bool  the boolean to check, null returns <code>true</code>
143         * @return <code>true</code> if the input is null or true
144         * @since 2.3
145         */
146        public static boolean isNotFalse(Boolean bool) {
147            return !isFalse(bool);
148        }
149    
150        //-----------------------------------------------------------------------
151        /**
152         * <p>Boolean factory that avoids creating new Boolean objecs all the time.</p>
153         * 
154         * <p>This method was added to JDK1.4 but is available here for earlier JDKs.</p>
155         *
156         * <pre>
157         *   BooleanUtils.toBooleanObject(false) = Boolean.FALSE
158         *   BooleanUtils.toBooleanObject(true)  = Boolean.TRUE
159         * </pre>
160         *
161         * @param bool  the boolean to convert
162         * @return Boolean.TRUE or Boolean.FALSE as appropriate
163         */
164        public static Boolean toBooleanObject(boolean bool) {
165            return bool ? Boolean.TRUE : Boolean.FALSE;
166        }
167        
168        /**
169         * <p>Converts a Boolean to a boolean handling <code>null</code>
170         * by returning <code>false</code>.</p>
171         *
172         * <pre>
173         *   BooleanUtils.toBoolean(Boolean.TRUE)  = true
174         *   BooleanUtils.toBoolean(Boolean.FALSE) = false
175         *   BooleanUtils.toBoolean(null)          = false
176         * </pre>
177         *
178         * @param bool  the boolean to convert
179         * @return <code>true</code> or <code>false</code>, 
180         *  <code>null</code> returns <code>false</code>
181         */
182        public static boolean toBoolean(Boolean bool) {
183            if (bool == null) {
184                return false;
185            }
186            return bool.booleanValue() ? true : false;
187        }
188        
189        /**
190         * <p>Converts a Boolean to a boolean handling <code>null</code>.</p>
191         * 
192         * <pre>
193         *   BooleanUtils.toBooleanDefaultIfNull(Boolean.TRUE, false) = true
194         *   BooleanUtils.toBooleanDefaultIfNull(Boolean.FALSE, true) = false
195         *   BooleanUtils.toBooleanDefaultIfNull(null, true)          = true
196         * </pre>
197         *
198         * @param bool  the boolean to convert
199         * @param valueIfNull  the boolean value to return if <code>null</code>
200         * @return <code>true</code> or <code>false</code>
201         */
202        public static boolean toBooleanDefaultIfNull(Boolean bool, boolean valueIfNull) {
203            if (bool == null) {
204                return valueIfNull;
205            }
206            return bool.booleanValue() ? true : false;
207        }
208        
209        // Integer to Boolean methods
210        //-----------------------------------------------------------------------
211        /**
212         * <p>Converts an int to a boolean using the convention that <code>zero</code>
213         * is <code>false</code>.</p>
214         * 
215         * <pre>
216         *   BooleanUtils.toBoolean(0) = false
217         *   BooleanUtils.toBoolean(1) = true
218         *   BooleanUtils.toBoolean(2) = true
219         * </pre>
220         *
221         * @param value  the int to convert
222         * @return <code>true</code> if non-zero, <code>false</code>
223         *  if zero
224         */
225        public static boolean toBoolean(int value) {
226            return value == 0 ? false : true;
227        }
228        
229        /**
230         * <p>Converts an int to a Boolean using the convention that <code>zero</code>
231         * is <code>false</code>.</p>
232         * 
233         * <pre>
234         *   BooleanUtils.toBoolean(0) = Boolean.FALSE
235         *   BooleanUtils.toBoolean(1) = Boolean.TRUE
236         *   BooleanUtils.toBoolean(2) = Boolean.TRUE
237         * </pre>
238         *
239         * @param value  the int to convert
240         * @return Boolean.TRUE if non-zero, Boolean.FALSE if zero,
241         *  <code>null</code> if <code>null</code>
242         */
243        public static Boolean toBooleanObject(int value) {
244            return value == 0 ? Boolean.FALSE : Boolean.TRUE;
245        }
246        
247        /**
248         * <p>Converts an Integer to a Boolean using the convention that <code>zero</code>
249         * is <code>false</code>.</p>
250         * 
251         * <p><code>null</code> will be converted to <code>null</code>.</p>
252         *
253         * <pre>
254         *   BooleanUtils.toBoolean(new Integer(0))    = Boolean.FALSE
255         *   BooleanUtils.toBoolean(new Integer(1))    = Boolean.TRUE
256         *   BooleanUtils.toBoolean(new Integer(null)) = null
257         * </pre>
258         *
259         * @param value  the Integer to convert
260         * @return Boolean.TRUE if non-zero, Boolean.FALSE if zero,
261         *  <code>null</code> if <code>null</code> input
262         */
263        public static Boolean toBooleanObject(Integer value) {
264            if (value == null) {
265                return null;
266            }
267            return value.intValue() == 0 ? Boolean.FALSE : Boolean.TRUE;
268        }
269        
270        /**
271         * <p>Converts an int to a boolean specifying the conversion values.</p>
272         * 
273         * <pre>
274         *   BooleanUtils.toBoolean(0, 1, 0) = false
275         *   BooleanUtils.toBoolean(1, 1, 0) = true
276         *   BooleanUtils.toBoolean(2, 1, 2) = false
277         *   BooleanUtils.toBoolean(2, 2, 0) = true
278         * </pre>
279         *
280         * @param value  the Integer to convert
281         * @param trueValue  the value to match for <code>true</code>
282         * @param falseValue  the value to match for <code>false</code>
283         * @return <code>true</code> or <code>false</code>
284         * @throws IllegalArgumentException if no match
285         */
286        public static boolean toBoolean(int value, int trueValue, int falseValue) {
287            if (value == trueValue) {
288                return true;
289            } else if (value == falseValue) {
290                return false;
291            }
292            // no match
293            throw new IllegalArgumentException("The Integer did not match either specified value");
294        }
295        
296        /**
297         * <p>Converts an Integer to a boolean specifying the conversion values.</p>
298         * 
299         * <pre>
300         *   BooleanUtils.toBoolean(new Integer(0), new Integer(1), new Integer(0)) = false
301         *   BooleanUtils.toBoolean(new Integer(1), new Integer(1), new Integer(0)) = true
302         *   BooleanUtils.toBoolean(new Integer(2), new Integer(1), new Integer(2)) = false
303         *   BooleanUtils.toBoolean(new Integer(2), new Integer(2), new Integer(0)) = true
304         *   BooleanUtils.toBoolean(null, null, new Integer(0))                     = true
305         * </pre>
306         *
307         * @param value  the Integer to convert
308         * @param trueValue  the value to match for <code>true</code>,
309         *  may be <code>null</code>
310         * @param falseValue  the value to match for <code>false</code>,
311         *  may be <code>null</code>
312         * @return <code>true</code> or <code>false</code>
313         * @throws IllegalArgumentException if no match
314         */
315        public static boolean toBoolean(Integer value, Integer trueValue, Integer falseValue) {
316            if (value == null) {
317                if (trueValue == null) {
318                    return true;
319                } else if (falseValue == null) {
320                    return false;
321                }
322            } else if (value.equals(trueValue)) {
323                return true;
324            } else if (value.equals(falseValue)) {
325                return false;
326            }
327            // no match
328            throw new IllegalArgumentException("The Integer did not match either specified value");
329        }
330        
331        /**
332         * <p>Converts an int to a Boolean specifying the conversion values.</p>
333         * 
334         * <pre>
335         *   BooleanUtils.toBooleanObject(0, 0, 2, 3) = Boolean.TRUE
336         *   BooleanUtils.toBooleanObject(2, 1, 2, 3) = Boolean.FALSE
337         *   BooleanUtils.toBooleanObject(3, 1, 2, 3) = null
338         * </pre>
339         *
340         * @param value  the Integer to convert
341         * @param trueValue  the value to match for <code>true</code>
342         * @param falseValue  the value to match for <code>false</code>
343         * @param nullValue  the value to to match for <code>null</code>
344         * @return Boolean.TRUE, Boolean.FALSE, or <code>null</code>
345         * @throws IllegalArgumentException if no match
346         */
347        public static Boolean toBooleanObject(int value, int trueValue, int falseValue, int nullValue) {
348            if (value == trueValue) {
349                return Boolean.TRUE;
350            } else if (value == falseValue) {
351                return Boolean.FALSE;
352            } else if (value == nullValue) {
353                return null;
354            }
355            // no match
356            throw new IllegalArgumentException("The Integer did not match any specified value");
357        }
358        
359        /**
360         * <p>Converts an Integer to a Boolean specifying the conversion values.</p>
361         * 
362         * <pre>
363         *   BooleanUtils.toBooleanObject(new Integer(0), new Integer(0), new Integer(2), new Integer(3)) = Boolean.TRUE
364         *   BooleanUtils.toBooleanObject(new Integer(2), new Integer(1), new Integer(2), new Integer(3)) = Boolean.FALSE
365         *   BooleanUtils.toBooleanObject(new Integer(3), new Integer(1), new Integer(2), new Integer(3)) = null
366         * </pre>
367         *
368         * @param value  the Integer to convert
369         * @param trueValue  the value to match for <code>true</code>,
370         *  may be <code>null</code>
371         * @param falseValue  the value to match for <code>false</code>,
372         *  may be <code>null</code>
373         * @param nullValue  the value to to match for <code>null</code>,
374         *  may be <code>null</code>
375         * @return Boolean.TRUE, Boolean.FALSE, or <code>null</code>
376         * @throws IllegalArgumentException if no match
377         */
378        public static Boolean toBooleanObject(Integer value, Integer trueValue, Integer falseValue, Integer nullValue) {
379            if (value == null) {
380                if (trueValue == null) {
381                    return Boolean.TRUE;
382                } else if (falseValue == null) {
383                    return Boolean.FALSE;
384                } else if (nullValue == null) {
385                    return null;
386                }
387            } else if (value.equals(trueValue)) {
388                return Boolean.TRUE;
389            } else if (value.equals(falseValue)) {
390                return Boolean.FALSE;
391            } else if (value.equals(nullValue)) {
392                return null;
393            }
394            // no match
395            throw new IllegalArgumentException("The Integer did not match any specified value");
396        }
397        
398        // Boolean to Integer methods
399        //-----------------------------------------------------------------------
400        /**
401         * <p>Converts a boolean to an int using the convention that
402         * <code>zero</code> is <code>false</code>.</p>
403         *
404         * <pre>
405         *   BooleanUtils.toInteger(true)  = 1
406         *   BooleanUtils.toInteger(false) = 0
407         * </pre>
408         *
409         * @param bool  the boolean to convert
410         * @return one if <code>true</code>, zero if <code>false</code>
411         */
412        public static int toInteger(boolean bool) {
413            return bool ? 1 : 0;
414        }
415        
416        /**
417         * <p>Converts a boolean to an Integer using the convention that
418         * <code>zero</code> is <code>false</code>.</p>
419         * 
420         * <pre>
421         *   BooleanUtils.toIntegerObject(true)  = new Integer(1)
422         *   BooleanUtils.toIntegerObject(false) = new Integer(0)
423         * </pre>
424         *
425         * @param bool  the boolean to convert
426         * @return one if <code>true</code>, zero if <code>false</code>
427         */
428        public static Integer toIntegerObject(boolean bool) {
429            return bool ? NumberUtils.INTEGER_ONE : NumberUtils.INTEGER_ZERO;
430        }
431        
432        /**
433         * <p>Converts a Boolean to a Integer using the convention that
434         * <code>zero</code> is <code>false</code>.</p>
435         *
436         * <p><code>null</code> will be converted to <code>null</code>.</p>
437         *
438         * <pre>
439         *   BooleanUtils.toIntegerObject(Boolean.TRUE)  = new Integer(1)
440         *   BooleanUtils.toIntegerObject(Boolean.FALSE) = new Integer(0)
441         * </pre>
442         *
443         * @param bool  the Boolean to convert
444         * @return one if Boolean.TRUE, zero if Boolean.FALSE, <code>null</code> if <code>null</code>
445         */
446        public static Integer toIntegerObject(Boolean bool) {
447            if (bool == null) {
448                return null;
449            }
450            return bool.booleanValue() ? NumberUtils.INTEGER_ONE : NumberUtils.INTEGER_ZERO;
451        }
452        
453        /**
454         * <p>Converts a boolean to an int specifying the conversion values.</p>
455         * 
456         * <pre>
457         *   BooleanUtils.toInteger(true, 1, 0)  = 1
458         *   BooleanUtils.toInteger(false, 1, 0) = 0
459         * </pre>
460         *
461         * @param bool  the to convert
462         * @param trueValue  the value to return if <code>true</code>
463         * @param falseValue  the value to return if <code>false</code>
464         * @return the appropriate value
465         */
466        public static int toInteger(boolean bool, int trueValue, int falseValue) {
467            return bool ? trueValue : falseValue;
468        }
469        
470        /**
471         * <p>Converts a Boolean to an int specifying the conversion values.</p>
472         * 
473         * <pre>
474         *   BooleanUtils.toInteger(Boolean.TRUE, 1, 0, 2)  = 1
475         *   BooleanUtils.toInteger(Boolean.FALSE, 1, 0, 2) = 0
476         *   BooleanUtils.toInteger(null, 1, 0, 2)          = 2
477         * </pre>
478         *
479         * @param bool  the Boolean to convert
480         * @param trueValue  the value to return if <code>true</code>
481         * @param falseValue  the value to return if <code>false</code>
482         * @param nullValue  the value to return if <code>null</code>
483         * @return the appropriate value
484         */
485        public static int toInteger(Boolean bool, int trueValue, int falseValue, int nullValue) {
486            if (bool == null) {
487                return nullValue;
488            }
489            return bool.booleanValue() ? trueValue : falseValue;
490        }
491        
492        /**
493         * <p>Converts a boolean to an Integer specifying the conversion values.</p>
494         * 
495         * <pre>
496         *   BooleanUtils.toIntegerObject(true, new Integer(1), new Integer(0))  = new Integer(1)
497         *   BooleanUtils.toIntegerObject(false, new Integer(1), new Integer(0)) = new Integer(0)
498         * </pre>
499         *
500         * @param bool  the to convert
501         * @param trueValue  the value to return if <code>true</code>,
502         *  may be <code>null</code>
503         * @param falseValue  the value to return if <code>false</code>,
504         *  may be <code>null</code>
505         * @return the appropriate value
506         */
507        public static Integer toIntegerObject(boolean bool, Integer trueValue, Integer falseValue) {
508            return bool ? trueValue : falseValue;
509        }
510        
511        /**
512         * <p>Converts a Boolean to an Integer specifying the conversion values.</p>
513         * 
514         * <pre>
515         *   BooleanUtils.toIntegerObject(Boolean.TRUE, new Integer(1), new Integer(0), new Integer(2))  = new Integer(1)
516         *   BooleanUtils.toIntegerObject(Boolean.FALSE, new Integer(1), new Integer(0), new Integer(2)) = new Integer(0)
517         *   BooleanUtils.toIntegerObject(null, new Integer(1), new Integer(0), new Integer(2))          = new Integer(2)
518         * </pre>
519         *
520         * @param bool  the Boolean to convert
521         * @param trueValue  the value to return if <code>true</code>,
522         *  may be <code>null</code>
523         * @param falseValue  the value to return if <code>false</code>,
524         *  may be <code>null</code>
525         * @param nullValue  the value to return if <code>null</code>,
526         *  may be <code>null</code>
527         * @return the appropriate value
528         */
529        public static Integer toIntegerObject(Boolean bool, Integer trueValue, Integer falseValue, Integer nullValue) {
530            if (bool == null) {
531                return nullValue;
532            }
533            return bool.booleanValue() ? trueValue : falseValue;
534        }
535        
536        // String to Boolean methods
537        //-----------------------------------------------------------------------
538        /**
539         * <p>Converts a String to a Boolean.</p>
540         * 
541         * <p><code>'true'</code>, <code>'on'</code> or <code>'yes'</code>
542         * (case insensitive) will return <code>true</code>.
543         * <code>'false'</code>, <code>'off'</code> or <code>'no'</code>
544         * (case insensitive) will return <code>false</code>.
545         * Otherwise, <code>null</code> is returned.</p>
546         *
547         * <pre>
548         *   BooleanUtils.toBooleanObject(null)    = null
549         *   BooleanUtils.toBooleanObject("true")  = Boolean.TRUE
550         *   BooleanUtils.toBooleanObject("false") = Boolean.FALSE
551         *   BooleanUtils.toBooleanObject("on")    = Boolean.TRUE
552         *   BooleanUtils.toBooleanObject("ON")    = Boolean.TRUE
553         *   BooleanUtils.toBooleanObject("off")   = Boolean.FALSE
554         *   BooleanUtils.toBooleanObject("oFf")   = Boolean.FALSE
555         *   BooleanUtils.toBooleanObject("blue")  = null
556         * </pre>
557         *
558         * @param str  the String to check
559         * @return the Boolean value of the string,
560         *  <code>null</code> if no match or <code>null</code> input
561         */
562        public static Boolean toBooleanObject(String str) {
563            if ("true".equalsIgnoreCase(str)) {
564                return Boolean.TRUE;
565            } else if ("false".equalsIgnoreCase(str)) {
566                return Boolean.FALSE;
567            } else if ("on".equalsIgnoreCase(str)) {
568                return Boolean.TRUE;
569            } else if ("off".equalsIgnoreCase(str)) {
570                return Boolean.FALSE;
571            } else if ("yes".equalsIgnoreCase(str)) {
572                return Boolean.TRUE;
573            } else if ("no".equalsIgnoreCase(str)) {
574                return Boolean.FALSE;
575            }
576            // no match
577            return null;
578        }
579    
580        /**
581         * <p>Converts a String to a Boolean throwing an exception if no match.</p>
582         *
583         * <pre>
584         *   BooleanUtils.toBooleanObject("true", "true", "false", "null")  = Boolean.TRUE
585         *   BooleanUtils.toBooleanObject("false", "true", "false", "null") = Boolean.FALSE
586         *   BooleanUtils.toBooleanObject("null", "true", "false", "null")  = null
587         * </pre>
588         *
589         * @param str  the String to check
590         * @param trueString  the String to match for <code>true</code>
591         *  (case sensitive), may be <code>null</code>
592         * @param falseString  the String to match for <code>false</code>
593         *  (case sensitive), may be <code>null</code>
594         * @param nullString  the String to match for <code>null</code>
595         *  (case sensitive), may be <code>null</code>
596         * @return the Boolean value of the string,
597         *  <code>null</code> if either the String matches <code>nullString</code>
598         *  or if <code>null</code> input and <code>nullString</code> is
599         *  <code>null</code>
600         * @throws IllegalArgumentException if the String doesn't match
601         */
602        public static Boolean toBooleanObject(String str, String trueString, String falseString, String nullString) {
603            if (str == null) {
604                if (trueString == null) {
605                    return Boolean.TRUE;
606                } else if (falseString == null) {
607                    return Boolean.FALSE;
608                } else if (nullString == null) {
609                    return null;
610                }
611            } else if (str.equals(trueString)) {
612                return Boolean.TRUE;
613            } else if (str.equals(falseString)) {
614                return Boolean.FALSE;
615            } else if (str.equals(nullString)) {
616                return null;
617            }
618            // no match
619            throw new IllegalArgumentException("The String did not match any specified value");
620        }
621    
622        // String to boolean methods
623        //-----------------------------------------------------------------------
624        /**
625         * <p>Converts a String to a boolean (optimised for performance).</p>
626         * 
627         * <p><code>'true'</code>, <code>'on'</code> or <code>'yes'</code>
628         * (case insensitive) will return <code>true</code>. Otherwise,
629         * <code>false</code> is returned.</p>
630         * 
631         * <p>This method performs 4 times faster (JDK1.4) than
632         * <code>Boolean.valueOf(String)</code>. However, this method accepts
633         * 'on' and 'yes' as true values.
634         *
635         * <pre>
636         *   BooleanUtils.toBoolean(null)    = false
637         *   BooleanUtils.toBoolean("true")  = true
638         *   BooleanUtils.toBoolean("TRUE")  = true
639         *   BooleanUtils.toBoolean("tRUe")  = true
640         *   BooleanUtils.toBoolean("on")    = true
641         *   BooleanUtils.toBoolean("yes")   = true
642         *   BooleanUtils.toBoolean("false") = false
643         *   BooleanUtils.toBoolean("x gti") = false
644         * </pre>
645         *
646         * @param str  the String to check
647         * @return the boolean value of the string, <code>false</code> if no match
648         */
649        public static boolean toBoolean(String str) {
650            // Previously used equalsIgnoreCase, which was fast for interned 'true'.
651            // Non interned 'true' matched 15 times slower.
652            // 
653            // Optimisation provides same performance as before for interned 'true'.
654            // Similar performance for null, 'false', and other strings not length 2/3/4.
655            // 'true'/'TRUE' match 4 times slower, 'tRUE'/'True' 7 times slower.
656            if (str == "true") {
657                return true;
658            }
659            if (str == null) {
660                return false;
661            }
662            switch (str.length()) {
663                case 2: {
664                    char ch0 = str.charAt(0);
665                    char ch1 = str.charAt(1);
666                    return 
667                        (ch0 == 'o' || ch0 == 'O') &&
668                        (ch1 == 'n' || ch1 == 'N');
669                }
670                case 3: {
671                    char ch = str.charAt(0);
672                    if (ch == 'y') {
673                        return 
674                            (str.charAt(1) == 'e' || str.charAt(1) == 'E') &&
675                            (str.charAt(2) == 's' || str.charAt(2) == 'S');
676                    }
677                    if (ch == 'Y') {
678                        return 
679                            (str.charAt(1) == 'E' || str.charAt(1) == 'e') &&
680                            (str.charAt(2) == 'S' || str.charAt(2) == 's');
681                    }
682                    return false;
683                }
684                case 4: {
685                    char ch = str.charAt(0);
686                    if (ch == 't') {
687                        return 
688                            (str.charAt(1) == 'r' || str.charAt(1) == 'R') &&
689                            (str.charAt(2) == 'u' || str.charAt(2) == 'U') &&
690                            (str.charAt(3) == 'e' || str.charAt(3) == 'E');
691                    }
692                    if (ch == 'T') {
693                        return 
694                            (str.charAt(1) == 'R' || str.charAt(1) == 'r') &&
695                            (str.charAt(2) == 'U' || str.charAt(2) == 'u') &&
696                            (str.charAt(3) == 'E' || str.charAt(3) == 'e');
697                    }
698                }
699            }
700            return false;
701        }
702        
703        /**
704         * <p>Converts a String to a Boolean throwing an exception if no match found.</p>
705         * 
706         * <p>null is returned if there is no match.</p>
707         *
708         * <pre>
709         *   BooleanUtils.toBoolean("true", "true", "false")  = true
710         *   BooleanUtils.toBoolean("false", "true", "false") = false
711         * </pre>
712         *
713         * @param str  the String to check
714         * @param trueString  the String to match for <code>true</code>
715         *  (case sensitive), may be <code>null</code>
716         * @param falseString  the String to match for <code>false</code>
717         *  (case sensitive), may be <code>null</code>
718         * @return the boolean value of the string
719         * @throws IllegalArgumentException if the String doesn't match
720         */
721        public static boolean toBoolean(String str, String trueString, String falseString) {
722            if (str == null) {
723                if (trueString == null) {
724                    return true;
725                } else if (falseString == null) {
726                    return false;
727                }
728            } else if (str.equals(trueString)) {
729                return true;
730            } else if (str.equals(falseString)) {
731                return false;
732            }
733            // no match
734            throw new IllegalArgumentException("The String did not match either specified value");
735        }
736    
737        // Boolean to String methods
738        //-----------------------------------------------------------------------
739        /**
740         * <p>Converts a Boolean to a String returning <code>'true'</code>,
741         * <code>'false'</code>, or <code>null</code>.</p>
742         * 
743         * <pre>
744         *   BooleanUtils.toStringTrueFalse(Boolean.TRUE)  = "true"
745         *   BooleanUtils.toStringTrueFalse(Boolean.FALSE) = "false"
746         *   BooleanUtils.toStringTrueFalse(null)          = null;
747         * </pre>
748         *
749         * @param bool  the Boolean to check
750         * @return <code>'true'</code>, <code>'false'</code>,
751         *  or <code>null</code>
752         */
753        public static String toStringTrueFalse(Boolean bool) {
754            return toString(bool, "true", "false", null);
755        }
756        
757        /**
758         * <p>Converts a Boolean to a String returning <code>'on'</code>,
759         * <code>'off'</code>, or <code>null</code>.</p>
760         * 
761         * <pre>
762         *   BooleanUtils.toStringOnOff(Boolean.TRUE)  = "on"
763         *   BooleanUtils.toStringOnOff(Boolean.FALSE) = "off"
764         *   BooleanUtils.toStringOnOff(null)          = null;
765         * </pre>
766         *
767         * @param bool  the Boolean to check
768         * @return <code>'on'</code>, <code>'off'</code>,
769         *  or <code>null</code>
770         */
771        public static String toStringOnOff(Boolean bool) {
772            return toString(bool, "on", "off", null);
773        }
774        
775        /**
776         * <p>Converts a Boolean to a String returning <code>'yes'</code>,
777         * <code>'no'</code>, or <code>null</code>.</p>
778         * 
779         * <pre>
780         *   BooleanUtils.toStringYesNo(Boolean.TRUE)  = "yes"
781         *   BooleanUtils.toStringYesNo(Boolean.FALSE) = "no"
782         *   BooleanUtils.toStringYesNo(null)          = null;
783         * </pre>
784         *
785         * @param bool  the Boolean to check
786         * @return <code>'yes'</code>, <code>'no'</code>,
787         *  or <code>null</code>
788         */
789        public static String toStringYesNo(Boolean bool) {
790            return toString(bool, "yes", "no", null);
791        }
792        
793        /**
794         * <p>Converts a Boolean to a String returning one of the input Strings.</p>
795         * 
796         * <pre>
797         *   BooleanUtils.toString(Boolean.TRUE, "true", "false", null)   = "true"
798         *   BooleanUtils.toString(Boolean.FALSE, "true", "false", null)  = "false"
799         *   BooleanUtils.toString(null, "true", "false", null)           = null;
800         * </pre>
801         *
802         * @param bool  the Boolean to check
803         * @param trueString  the String to return if <code>true</code>,
804         *  may be <code>null</code>
805         * @param falseString  the String to return if <code>false</code>,
806         *  may be <code>null</code>
807         * @param nullString  the String to return if <code>null</code>,
808         *  may be <code>null</code>
809         * @return one of the three input Strings
810         */
811        public static String toString(Boolean bool, String trueString, String falseString, String nullString) {
812            if (bool == null) {
813                return nullString;
814            }
815            return bool.booleanValue() ? trueString : falseString;
816        }
817        
818        // boolean to String methods
819        //-----------------------------------------------------------------------
820        /**
821         * <p>Converts a boolean to a String returning <code>'true'</code>
822         * or <code>'false'</code>.</p>
823         * 
824         * <pre>
825         *   BooleanUtils.toStringTrueFalse(true)   = "true"
826         *   BooleanUtils.toStringTrueFalse(false)  = "false"
827         * </pre>
828         *
829         * @param bool  the Boolean to check
830         * @return <code>'true'</code>, <code>'false'</code>,
831         *  or <code>null</code>
832         */
833        public static String toStringTrueFalse(boolean bool) {
834            return toString(bool, "true", "false");
835        }
836        
837        /**
838         * <p>Converts a boolean to a String returning <code>'on'</code>
839         * or <code>'off'</code>.</p>
840         * 
841         * <pre>
842         *   BooleanUtils.toStringOnOff(true)   = "on"
843         *   BooleanUtils.toStringOnOff(false)  = "off"
844         * </pre>
845         *
846         * @param bool  the Boolean to check
847         * @return <code>'on'</code>, <code>'off'</code>,
848         *  or <code>null</code>
849         */
850        public static String toStringOnOff(boolean bool) {
851            return toString(bool, "on", "off");
852        }
853        
854        /**
855         * <p>Converts a boolean to a String returning <code>'yes'</code>
856         * or <code>'no'</code>.</p>
857         * 
858         * <pre>
859         *   BooleanUtils.toStringYesNo(true)   = "yes"
860         *   BooleanUtils.toStringYesNo(false)  = "no"
861         * </pre>
862         *
863         * @param bool  the Boolean to check
864         * @return <code>'yes'</code>, <code>'no'</code>,
865         *  or <code>null</code>
866         */
867        public static String toStringYesNo(boolean bool) {
868            return toString(bool, "yes", "no");
869        }
870        
871        /**
872         * <p>Converts a boolean to a String returning one of the input Strings.</p>
873         * 
874         * <pre>
875         *   BooleanUtils.toString(true, "true", "false")   = "true"
876         *   BooleanUtils.toString(false, "true", "false")  = "false"
877         * </pre>
878         *
879         * @param bool  the Boolean to check
880         * @param trueString  the String to return if <code>true</code>,
881         *  may be <code>null</code>
882         * @param falseString  the String to return if <code>false</code>,
883         *  may be <code>null</code>
884         * @return one of the two input Strings
885         */
886        public static String toString(boolean bool, String trueString, String falseString) {
887            return bool ? trueString : falseString;
888        }
889        
890        // xor methods
891        // ----------------------------------------------------------------------
892        /**
893         * <p>Performs an xor on a set of booleans.</p>
894         *
895         * <pre>
896         *   BooleanUtils.xor(new boolean[] { true, true })   = false
897         *   BooleanUtils.xor(new boolean[] { false, false }) = false
898         *   BooleanUtils.xor(new boolean[] { true, false })  = true
899         * </pre>
900         *
901         * @param array  an array of <code>boolean<code>s
902         * @return <code>true</code> if the xor is successful.
903         * @throws IllegalArgumentException if <code>array</code> is <code>null</code>
904         * @throws IllegalArgumentException if <code>array</code> is empty.
905         */
906        public static boolean xor(boolean[] array) {
907            // Validates input
908            if (array == null) {
909                throw new IllegalArgumentException("The Array must not be null");
910            } else if (array.length == 0) {
911                throw new IllegalArgumentException("Array is empty");
912            }
913    
914            // Loops through array, comparing each item
915            int trueCount = 0;
916            for (int i = 0; i < array.length; i++) {
917                // If item is true, and trueCount is < 1, increments count
918                // Else, xor fails
919                if (array[i]) {
920                    if (trueCount < 1) {
921                        trueCount++;
922                    } else {
923                        return false;
924                    }
925                }
926            }
927    
928            // Returns true if there was exactly 1 true item
929            return trueCount == 1;
930        }
931    
932        /**
933         * <p>Performs an xor on an array of Booleans.</p>
934         * 
935         * <pre>
936         *   BooleanUtils.xor(new Boolean[] { Boolean.TRUE, Boolean.TRUE })   = Boolean.FALSE
937         *   BooleanUtils.xor(new Boolean[] { Boolean.FALSE, Boolean.FALSE }) = Boolean.FALSE
938         *   BooleanUtils.xor(new Boolean[] { Boolean.TRUE, Boolean.FALSE })  = Boolean.TRUE
939         * </pre>
940         *
941         * @param array  an array of <code>Boolean<code>s
942         * @return <code>true</code> if the xor is successful.
943         * @throws IllegalArgumentException if <code>array</code> is <code>null</code>
944         * @throws IllegalArgumentException if <code>array</code> is empty.
945         * @throws IllegalArgumentException if <code>array</code> contains a <code>null</code>
946         */
947        public static Boolean xor(Boolean[] array) {
948            if (array == null) {
949                throw new IllegalArgumentException("The Array must not be null");
950            } else if (array.length == 0) {
951                throw new IllegalArgumentException("Array is empty");
952            }
953            boolean[] primitive = null;
954            try {
955                primitive = ArrayUtils.toPrimitive(array);
956            } catch (NullPointerException ex) {
957                throw new IllegalArgumentException("The array must not contain any null elements");
958            }
959            return xor(primitive) ? Boolean.TRUE : Boolean.FALSE;
960        }
961    
962    }