概述:

有些场景需要对 数据结构中的数据进行排序,java中提供了sort方法, 可以通过自定义的comparator,指定排序方式,以下为例子及实现

使用

例子1

: comparator 比较 list 中对象属性

package JavaContainer.comparator;//https://www.cnblogs.com/rossoneri/p/4549529.htmlimport org.junit.Test;import java.util.*;//根据姓名排序class ComparatorName implements Comparator
    
     {    boolean is_Ascend;    public ComparatorName(boolean b) {        // TODO Auto-generated constructor stub        is_Ascend = b;    }    @Override    public int compare(PersonComparaBean o1, PersonComparaBean o2) {        //o1  o2 分别对应容器中前一个对象和后一个对象        if (is_Ascend)            return o1.getName().compareTo(o2.getName());        else            return o2.getName().compareTo(o1.getName());    }}//根据id排序class ComparatorId implements Comparator
     
      {    private boolean aescOrDesc;    public ComparatorId(boolean aescOrDesc) {        this.aescOrDesc = aescOrDesc;    }    @Override    public int compare(PersonComparaBean o1 , PersonComparaBean o2) {        int a, b;        if (aescOrDesc) {            a = o1.getId();            b = o2.getId();        } else {            a = o2.getId();            b = o1.getId();        }        if (a > b)            return 1;        else if (a == b)            return 0;        else            return -1;    }}public class ComparatorDemo1 {    @Test    public void sortByNameOrId(){        PersonComparaBean personComparaBean1 = new PersonComparaBean();        personComparaBean1.setId(1);        personComparaBean1.setName("ZZZZ");        PersonComparaBean personComparaBean2 = new PersonComparaBean();        personComparaBean2.setId(5);        personComparaBean2.setName("CCCC");        PersonComparaBean personComparaBean4 = new PersonComparaBean();        personComparaBean4.setId(2);        personComparaBean4.setName("DDDD");        PersonComparaBean personComparaBean3 = new PersonComparaBean();        personComparaBean3.setId(8);        personComparaBean3.setName("AAAA");        List
      
        list = new ArrayList<>();        list.add(personComparaBean1);        list.add(personComparaBean2);        list.add(personComparaBean3);        list.add(personComparaBean4);        for (PersonComparaBean personComparaBean : list){            System.out.println("原: "+personComparaBean);        }        /*  原: PersonComparaBean{id='1', name='ZZZZ'}            原: PersonComparaBean{id='5', name='CCCC'}            原: PersonComparaBean{id='8', name='AAAA'}            原: PersonComparaBean{id='2', name='DDDD'}*/        Collections.sort(list,new ComparatorId(true));        for (PersonComparaBean personComparaBean : list){            System.out.println("id: "+personComparaBean);        }        /*id: PersonComparaBean{id='1', name='ZZZZ'}        id: PersonComparaBean{id='2', name='DDDD'}        id: PersonComparaBean{id='5', name='CCCC'}        id: PersonComparaBean{id='8', name='AAAA'}*/        Collections.sort(list,new ComparatorName(true));        for (PersonComparaBean personComparaBean : list){            System.out.println("name: "+personComparaBean);        }        /*name: PersonComparaBean{id='8', name='AAAA'}        name: PersonComparaBean{id='5', name='CCCC'}        name: PersonComparaBean{id='2', name='DDDD'}        name: PersonComparaBean{id='1', name='ZZZZ'}*/    }}
      
     
    

例子2

: 比较二位数组 comparator

package JavaContainer.comparator;import org.junit.Test;import java.util.Arrays;import java.util.Comparator;//二维数组第二位比较(如果想要先判断第一位,然后第二位,可以在比较器中再加判断条件对比)public class ComparatorDemo2 {    @Test    public void test() {        int[][] nums = {
   {1, 2}, {2, 3}, {1, 1}};        for (int[] num : nums) {            for (int num1 : num) {                System.out.print(num1);            }            System.out.println("  ");        }        Arrays.sort(nums, new Comparator
    
     () {            @Override            public int compare(int[] o1, int[] o2) {                return o1[1] - o2[1];            }        });        for (int[] num : nums) {            for (int num1 : num) {                System.out.print(num1);            }            System.out.println("  ");        }        /*12            23            11            11            12            23 */    }}