Java常用的工具类实例代码分析

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一、FileUtils

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 asList = Arrays.asList(listFiles);    for(File file:listFiles) {        System.out.println(file);    }    Collections.sort(asList, new Comparator() {        @Override        public int compare(File o1, File o2) {            if(o1.lastModified()o2.lastModified()) {                return 1;            }else {                return 0;            }        }    });    System.out.println("sort...");    for(File file:listFiles) {        System.out.println(file+","+file.lastModified());    }}

二、StringUtil

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或或    String chomp = StringUtils.chomp(str);    System.out.println(chomp);    //chop剔除字符串最后一个字符（如果最后一个是或或也剔除掉）    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}

三、CollectionUtils

private static void collectionUtilsTest() {    List list = new ArrayList();    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 list2 = new ArrayList();    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 list2 = new ArrayList();    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>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> list3 = new ArrayList>();    List> list4 = new ArrayList>();    Map map1 = new HashMap();    map1.put("name", "zhangsan");    map1.put("age", 18);    map1.put("address", "dalian");    Map map2 = new HashMap();    map2.put("name", "张三");    map2.put("age", "十八");    map2.put("address", "大连");    list3.add(map1);    list3.add(map2);     Map map3 = new HashMap();    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 list2 = new ArrayList();    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 list2 = new ArrayList();    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 list2 = new ArrayList();    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);}

四、ArrayUtils

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}

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