今天小编给大家分享的是Java常用工具类汇总以及示例代码，相信很多人都不太了解，为了让大家更加了解，所以给大家总结了以下内容，一起往下看吧。一定会有所收获的哦。
Java是什么
Java是一门面向对象编程语言，可以编写桌面应用程序、Web应用程序、分布式系统和嵌入式系统应用程序。
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<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()); }}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\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}三、CollectionUtils
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);}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}关于Java常用工具类汇总以及示例代码就分享到这里了，希望以上内容可以对大家有一定的参考价值，可以学以致用。如果喜欢本篇文章，不妨把它分享出去让更多的人看到。
