Java中实现Comparator接口和用法实例（简明易懂）

在java中，如果要对集合对象或数组对象进行排序，需要实现Comparator接口以达到我们想要的目标。

接下来我们模拟下在集合对象中对日期属性进行排序

一、实体类Step

package com.ljq.entity;



public class Step{
  
  private String acceptTime = "";
  
  private String acceptAddress = "";

  public Step() {
    super();
  }

  public Step(String acceptTime, String acceptAddress) {
    super();
    this.acceptTime = acceptTime;
    this.acceptAddress = acceptAddress;
  }

  public String getAcceptTime() {
    return acceptTime;
  }

  public void setAcceptTime(String acceptTime) {
    this.acceptTime = acceptTime;
  }

  public String getAcceptAddress() {
    return acceptAddress;
  }

  public void setAcceptAddress(String acceptAddress) {
    this.acceptAddress = acceptAddress;
  }

}

二、实现Comparator接口

package com.ljq.entity;

import java.util.Comparator;
import java.util.Date;

import com.ljq.util.UtilTool;


public class StepComparator implements Comparator{

  
  @Override
  public int compare(Step o1, Step o2) {
    Date acceptTime1=UtilTool.strToDate(o1.getAcceptTime(), null);
    Date acceptTime2=UtilTool.strToDate(o2.getAcceptTime(), null);
    
    //对日期字段进行升序，如果欲降序可采用before方法
    if(acceptTime1.after(acceptTime2)) return 1;
    return -1;
  }

}

三、测试

package junit;

import java.util.Collection;
import java.util.Collections;
import java.util.List;

import org.junit.Test;


public class StepComparatorTest {

  @Test
  public void sort() throws Exception{
    List steps=new ArrayList;
    //对集合对象进行排序
     StepComparator comparator=new StepComparator();
    Collections.sort(steps, comparator);
    if(steps!=null&&steps.size()>0){
      for(Step step:steps){
 System.out.println(step.getAcceptAddress());
 System.out.println(step.getAcceptTime());
      }
    }

  }
}