Java常用工具类汇总 附示例代码

private static void fileUtilsTest() {

     try {

         //读取文件内容

         String readFileToString = FileUtils.readFileToString( new File( "D:\\guor\\data\\test20211022000000.txt" ));

         System.out.println(readFileToString);

         //删除文件夹

         FileUtils.deleteDirectory( new File( "D:\\guor1\\data1" ));

         FileUtils.deleteQuietly( new File( "D:\\guor\\data" ));

         //清空文件夹

         FileUtils.cleanDirectory( new File( "D:\\guor\\data" ));

         //判断文件内容是否一致

         boolean contentEquals = FileUtils.contentEquals( new File( "D:\\guor\\data\\test20211022000000.txt" ), new File( "D:\\guor\\data\\testNew20211021000000.txt" ));

         boolean contentEquals2 = FileUtils.contentEquals( new File( "D:\\guor\\data\\中文20211021100000.txt" ), new File( "D:\\guor\\data\\中文New20211022100000.txt" ));

         System.out.println(contentEquals+ "," +contentEquals2);

         //拷贝特定类型的文件

         FileUtils.copyDirectory( new File( "D:\\guor\\data" ), new File( "D:\\guor\\data2" ), new FileFilter() {

             @Override

             public boolean accept(File pathname) {

                 if (pathname.getName().startsWith( "test" )) {

                     return true ;

                 }

                 return false ;

             }

         });

         FileUtils.moveDirectory( new File( "D:\\guor\\data" ), new File( "D:\\guor\\data3" ));

         FileUtils.moveFileToDirectory( new File( "D:\\guor\\data" ), new File( "D:\\guor\\data3" ), true );

         FileUtils.moveToDirectory( new File( "D:\\guor\\data" ), new File( "D:\\guor\\data4" ), true );

         boolean directoryContains = FileUtils.directoryContains( new File( "D:\\guor\\data" ), new File( "D:\\guor\\data\\test20211022000000.txt" ));

         System.out.println(directoryContains);

         directoryContains = FileUtils.directoryContains( new File( "D:\\guor\\data" ), new File( "*.txt" ));

         System.out.println(directoryContains);

         //获取某文件夹下特定格式文件

         File[] listFiles = new File( "D:\\guor\\data" ).listFiles( new FilenameFilter() {

             @Override

             public boolean accept(File dir, String name) {

                 return name.startsWith( "test" );

             }

         });

         System.out.println(Arrays.toString(listFiles));

         //获取系统temp文件夹路径

         File tempDirectory = FileUtils.getTempDirectory();

         System.out.println(tempDirectory);

         //获取系统用户文件夹路径

         File userDirectory = FileUtils.getUserDirectory();

         System.out.println(userDirectory);

         //查看是否是新建的文件夹

         SimpleDateFormat sdf = new SimpleDateFormat( "yyyyMMddHHmmss" );

         Date parse = sdf.parse( "20210206134900" );

         boolean fileNewer = FileUtils.isFileNewer( new File( "D:\\guor\\data" ), parse);

         System.out.println(fileNewer);

         //更新文件修改时间，如果不存在，则新建；

         FileUtils.touch( new File( "D:\\guor\\data\\test20211022000000.txt" ));

         //延迟查看文件是否存在

         boolean waitFor = FileUtils.waitFor( new File( "D:\\guor\\data\\testNew20211021000000.txt" ), 5 );

         System.out.println(waitFor);

     } catch (Exception e) {

         System.out.println(e);

     }

}

//根据文件修改时间排序

public static void test02() {

     String dir = "D:\\data" ;

     File[] listFiles = new File(dir).listFiles();

     List<File> asList = Arrays.asList(listFiles);

     for (File file:listFiles) {

         System.out.println(file);

     }

     Collections.sort(asList, new Comparator<File>() {

         @Override

         public int compare(File o1, File o2) {

             if (o1.lastModified()<o2.lastModified()) {

                 return - 1 ;

             } else if (o1.lastModified()>o2.lastModified()) {

                 return 1 ;

             } else {

                 return 0 ;

             }

         }

     });

     System.out.println( "sort..." );

     for (File file:listFiles) {

         System.out.println(file+ "," +file.lastModified());

     }

}

private static void stringUtilsTest() {

     String str = "hello world" ;

     //将第一个字符大写

     String capitalize = StringUtils.capitalize(str);

     System.out.println(capitalize); //Hello

     //两边空格补齐

     String center = StringUtils.center(str, 7 );

     System.out.println(center); // hello

     String center = StringUtils.center(str, 7 , "*" );

     System.out.println(center); //*hello*

     //chomp剔除字符串最后一个是\n或\r\或\r\n

     String chomp = StringUtils.chomp(str);

     System.out.println(chomp);

     //chop剔除字符串最后一个字符（如果最后一个是\n或\r\或\r\n也剔除掉）

     String chop = StringUtils.chop(str);

     System.out.println(chop); //hello worl

     //是否包含任意字符

     boolean containsAny = StringUtils.containsAny(str, "W" );

     System.out.println(containsAny);

     //是否包含任意字符，忽略大小写

     containsAny = StringUtils.containsIgnoreCase(str, "W" );

     System.out.println(containsAny);

     //有意思

     int indexOfAnyBut = StringUtils.indexOfAnyBut(str, "hello orld" );

     System.out.println(indexOfAnyBut);

     //两个字符串从第几位开始不同

     int indexOfDifference = StringUtils.indexOfDifference(str, str);

     System.out.println(indexOfDifference);

     indexOfDifference = StringUtils.indexOfDifference(str, str+ "zs" );

     System.out.println(indexOfDifference);

     indexOfDifference = StringUtils.indexOfDifference(str, "he llo" );

     System.out.println(indexOfDifference);

     //判断是否是正整数

     boolean isNumeric = StringUtils.isNumeric(str);

     System.out.println(isNumeric); //false

     isNumeric = StringUtils.isNumeric( "1234dd" );

     System.out.println( "1234dd:" +isNumeric); //false

     isNumeric = StringUtils.isNumeric( "1234 " );

     System.out.println( "1234 :" +isNumeric); //false

     isNumeric = StringUtils.isNumeric( "1.234" );

     System.out.println( "1.234:" +isNumeric); //false

     isNumeric = StringUtils.isNumeric( "1234" );

     System.out.println( "1234:" + isNumeric); //true

     isNumeric = StringUtils.isNumeric( "-1234" );

     System.out.println( "-1234:" + isNumeric); //false

     //判断是否是正整数或空格

     boolean isNumeric = StringUtils.isNumericSpace(str);

     //将数组变为字符串，并添加字符进行分割

     Object[] array = new Object[] { "zs" , 18 , "男" , 666 , 777 };

     String join = StringUtils.join(array);

     System.out.println(Arrays.toString(array));

     join = StringUtils.join(array, "*" );

     System.out.println(join);

     Object[] array = new Object[] { "zs" , 18 , "男" , 666 , 777 };

     String join = StringUtils.join(array, ";" , 2 , 5 );

     System.out.println(join);

     String remove = StringUtils.remove(str, "hello" );

     System.out.println(remove); // world

     String repeat = StringUtils.repeat(str, 3 );

     System.out.println(repeat); //hello worldhello worldhello world

     repeat = StringUtils.repeat(str, "," , 3 );

     System.out.println(repeat); //hello world,hello world,hello world

     //分别替换

     String[] list =  new String[] { "hello" , "girl" };

     String[] replacementList =  new String[] { "say" , "woman" };

     String str2 = "hello world,hello boy,hello girl." ;

     String replaceEach = StringUtils.replaceEach(str2, list, replacementList);

     System.out.println(replaceEach); //say world,say boy,say woman.

     //只替换第一个匹配的字符串

     String replaceOnce = StringUtils.replaceOnce( "hello world,hello boy,hello girl." , "hello" , "say" );

     System.out.println(replaceOnce); //say world,hello boy,hello girl.

     //截取某字符后面的部分

     String substringAfterLast = StringUtils.substringAfterLast( "hello world,hello boy,hello girl." , " " );

     System.out.println(substringAfterLast); //girl.

     String substringBeforeLast = StringUtils.substringBeforeLast( "hello world,hello boy,hello girl." , " " );

     System.out.println(substringBeforeLast); //hello world,hello boy,hello

}

private static void collectionUtilsTest() {

     List<String> list = new ArrayList<String>();

     list.add( "zhangsan" );

     list.add( "dalian" );

     list.add( "gateway" );

     list.add( "gateway" );

     list.add( "28" );

     list.add( "35" );

     //查找第一个符合条件的元素

     Object find = CollectionUtils.find(list, new Predicate() {

         @Override

         public boolean evaluate(Object arg0) {

             if (StringUtils.isNumeric(arg0.toString())) {

                 return false ;

             }

             return true ;

         }

     });

     //排除不符合条件的元素

     Collection select = CollectionUtils.select(list, new Predicate() {

         @Override

         public boolean evaluate(Object arg0) {

             if (StringUtils.isNumeric(arg0.toString())) {

                 return false ;

             }

             return true ;

         }

     });

     System.out.println(list); //[zhangsan, dalian, 28]

     System.out.println(find); //zhangsan

     System.out.println(select); //[zhangsan, dalian]

     List<String> list2 = new ArrayList<String>();

     list2.add( "zhangsan" );

     list2.add( "dalian2" );

     list2.add( "282" );

     //查看两个集合中是否有相同的元素

     boolean containsAny = CollectionUtils.containsAny(list, list2);

     System.out.println(containsAny); //true

     //查找集合中某元素的个数

     int countMatches = CollectionUtils.countMatches(list, new Predicate() {

         @Override

         public boolean evaluate(Object arg0) {

             if (StringUtils.isNumeric(arg0.toString())) {

                 return true ;

             }

             return false ;

         }

     });

     System.out.println(countMatches);

     //查找集合中是否存在某元素

     boolean exists = CollectionUtils.exists(list, new Predicate() {

         @Override

         public boolean evaluate(Object arg0) {

             if (StringUtils.isNumeric(arg0.toString())) {

                 return true ;

             }

             return false ;

         }

     });

     System.out.println(exists);

     //删除集合中的某些元素

     System.out.println(list); //[zhangsan, dalian, 打法, 28, 35]

     CollectionUtils.filter(list, new Predicate() {

         @Override

         public boolean evaluate(Object arg0) {

             if (StringUtils.isNumeric(arg0.toString())) {

                 return false ;

             }

             return true ;

         }

     });

     System.out.println(list); //[zhangsan, dalian, 打法]

     //查找集合中符合条件的第一个元素

     Object find = CollectionUtils.find(list, new Predicate() {

         @Override

         public boolean evaluate(Object arg0) {

             if (StringUtils.isNumeric(arg0.toString())) {

                 return false ;

             }

             return true ;

         }

     });

     System.out.println(find); //zhangsan

     //闭包回调函数

     System.out.println(list);

     CollectionUtils.forAllDo(list, new Closure() {

         @Override

         public void execute(Object arg0) {

             if (StringUtils.isNumeric(arg0.toString())) {

                 work(arg0);

             }

         }

     });

     System.out.println(list);

     //查找集合中元素的个数

     System.out.println(list); //[zhangsan, dalian, gateway, gateway, 28, 35]

     Map cardinalityMap = CollectionUtils.getCardinalityMap(list);

     System.out.println(cardinalityMap); //{35=1, 28=1, zhangsan=1, dalian=1, gateway=2}

     //查找两个集合中的相同元素

     List<String> list2 = new ArrayList<String>();

     list2.add( "lisi" );

     list2.add( "beijing" );

     list2.add( "gateway" );

     list.add( "19" );

     Collection intersection = CollectionUtils.intersection(list, list2);

     System.out.println(intersection);

     //获取两个List<Map<String, Object>>中相同的部分，可以用于对比两个库中的相同表数据是否相等

     List<Map<String, Object>> list3 = new ArrayList<Map<String,Object>>();

     List<Map<String, Object>> list4 = new ArrayList<Map<String,Object>>();

     Map<String, Object> map1 = new HashMap<String, Object>();

     map1.put( "name" , "zhangsan" );

     map1.put( "age" , 18 );

     map1.put( "address" , "dalian" );

     Map<String, Object> map2 = new HashMap<String, Object>();

     map2.put( "name" , "张三" );

     map2.put( "age" , "十八" );

     map2.put( "address" , "大连" );

     list3.add(map1);

     list3.add(map2);

     Map<String, Object> map3 = new HashMap<String, Object>();

     map3.put( "name" , "李四" );

     map3.put( "age" , "十八" );

     map3.put( "address" , "大连" );

     list4.add(map2);

     list4.add(map1);

     list3.add(map3);

     System.out.println(list3);

     System.out.println(list4);

     Collection intersection = CollectionUtils.intersection(list3, list4);

     System.out.println(intersection); //[{address=dalian, name=zhangsan, age=18}]

     //判断两个集合是否相同

     boolean equalCollection = CollectionUtils.isEqualCollection(list3, list4);

     System.out.println(equalCollection);

     判断param2是否包含param1，且不能完全相同

     System.out.println(list3); //[{address=dalian, name=zhangsan, age=18}, {address=大连, name=张三, age=十八}, {address=大连, name=李四, age=十八}]

     System.out.println(list4); //[{address=大连, name=张三, age=十八}, {address=dalian, name=zhangsan, age=18}]

     boolean properSubCollection = CollectionUtils.isProperSubCollection(list4, list3);

     System.out.println(properSubCollection); //true

     //断定某集合是否含有某元素，如果包含则抛异常（我觉得应该少用为妙）

     System.out.println(list); //[zhangsan, dalian, gateway, gateway, 28, 35]

     Collection predicatedCollection = CollectionUtils.predicatedCollection(list, new Predicate() {

         @Override

         public boolean evaluate(Object object) {

             if (StringUtils.isNumeric(object.toString())) {

                 return false ;

             }

             return true ;

         }

     });

     System.out.println(predicatedCollection); //Exception in thread "main" java.lang.IllegalArgumentException: Cannot add Object '28' - Predicate rejected it

     List<String> list2 = new ArrayList<String>();

     list2.add( "gateway" );

     System.out.println(list);

     System.out.println(list2);

     //删除list1中的list2

     Collection removeAll = CollectionUtils.removeAll(list, list2);

     System.out.println(removeAll);

     //反转数组

     String[] array = new String[] { "zs" , "ls" , "ww" };

     System.out.println(StringUtils.join(array, "," )); //zs,ls,ww

     CollectionUtils.reverseArray(array);

     System.out.println(StringUtils.join(array, "," )); //ww,ls,zs

     删除list1中的list2

     List<String> list2 = new ArrayList<String>();

     list2.add( "zhangsan" );

     list2.add( "dalian" );

     Collection subtract = CollectionUtils.subtract(list, list2);

     System.out.println(subtract);

     //更改集合中的特定值

     Collection collect = CollectionUtils.collect(list, new Transformer() {

         @Override

         public Object transform(Object arg0) {

             if (StringUtils.isNumeric(arg0.toString())) {

                 return 15 ;

             }

             return arg0;

         }

     });

     System.out.println(list); //[zhangsan, dalian, 28, 35]

     System.out.println(collect); //[zhangsan, dalian, 15, 15]

     //更改集合中的特定值，改变集合本身

     System.out.println(list); //[zhangsan, dalian, gateway, gateway, 28, 35]

     CollectionUtils.transform(list, new Transformer() {

         @Override

         public Object transform(Object input) {

             if (StringUtils.isNumeric(input.toString())) {

                 return 15 ;

             }

             return input;

         }

     });

     System.out.println(list); //[zhangsan, dalian, gateway, gateway, 15, 15]

     List<String> list2 = new ArrayList<String>();

     list2.add( "docker" );

     list2.add( "zhangsan" );

     System.out.println(list);

     System.out.println(list2);

     //将list和list2中的元素合并，但去除list2中的重复元素

     Collection union = CollectionUtils.union(list, list2);

     System.out.println(union);

}

private static void work(Object obj){

     System.out.println( "闭包回调函数:我是数字，" +obj);

}

private static void arrayUtilsTest() {

     String[] array = new String[] { "zs" , "ls" };

     //增加元素

     Object[] add = ArrayUtils.add(array, "ww" );

     System.out.println(StringUtils.join(add, "," )); //zs,ls,ww

     //合并数组

     String[] array2 = new String[] { "ww" , "ss" };

     Object[] addAll = ArrayUtils.addAll(array1, array2);

     System.out.println(StringUtils.join(addAll, "," )); //zs,ls,ww,ss

     //克隆数组

     Object[] clone = ArrayUtils.clone(array);

     System.out.println(StringUtils.join(clone, "," )); //zs,ls

     boolean contains = ArrayUtils.contains(array, "ww" );

     boolean contains1 = ArrayUtils.contains(array, "zs" );

     System.out.println(contains+ "," +contains1); //false,true

}