java对集合中某个字段进行排序

下面首先我们先创建一个测试类，这里重点说一哈，可以实现一个Comparable接口重写compareTo

public class TestA implements Comparable { private String name; private Integer age; public TestA(String name, Integer age) { super(); this.name = name; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } @Override public String toString() { return "TestA [name=" + name + ", age=" + age + "]"; } @Override public int compareTo(TestA o) { return this.age.compareTo(o.getAge()); } }

校验：

import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List; public class DemoTest { public static void main(String[] args) { TestA testA1 = new TestA("老张", 3); TestA testA2 = new TestA("老李", 1); TestA testA3 = new TestA("老王", 2); List list = new ArrayList<>(); list.add(testA1); list.add(testA2); list.add(testA3); System.out.println("排序前--:"+list.toString()); Collections.sort(list, new Comparator() { @Override public int compare(TestA o1, TestA o2) { //升序 return o1.getAge().compareTo(o2.getAge()); } }); System.out.println("升序排序后--:"+list.toString()); Collections.sort(list, new Comparator() { @Override public int compare(TestA o1, TestA o2) { //降序 return o2.getAge().compareTo(o1.getAge()); } }); System.out.println("降序排序后--:"+list.toString()); } }

结果：