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本篇文章将为您介绍在 Java 开发中较常见的几种工具类，附带具体代码实例，希望可以帮助到你的学习。
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());
}
}
//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
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<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 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
}以上就是关于Java中几种常见工具类以及各自的代码实例的全部内容,想要了解更多和Java常用工具类相关内容请搜索W3Cschool以前的文章或继续浏览下面的相关文章，希望大家以后多多支持！
