如何根据对象里面的的某1个字段对List排序

[sklyn1984]

对象类型List<User>,想根据里面的percent字段排序，percent是字符串类型百分比形如"25.12%"，想根据这个字段由高到低排序！

[zhoujiaolongde]

我这里有个sample
People.java

package com.zhoujl.test;

/**
 * @author zhoujl
 * 2011/12/28 10:11:04
 */
public class People implements Comparable {

	private int age;
	private String name;
	
	public People(int age,String name) {
		this.age = age;
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	/* 
	 * 在这里写比较的逻辑return 1就是大于  return 0就是小于
	 */
	@Override
	public int compareTo(Object people) {
		
		if(this.age>((People)people).age) {
			return 1;
		}else { 
			return 0;
		}
	}

	@Override
	public String toString() {
		return "Name:" +name+"\n"+"Age:"+age+"\n";
	}
	
	
	
	
}

TestSort.java

package com.zhoujl.test;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * @author zhoujl
 * 2011/12/28 10:10:47
 */
public class TestSort {

	@SuppressWarnings("unchecked")
	public static void main(String[] args) {
		List<People> list = new ArrayList<People>();
		
		People people1 = new People(12,"zhou");
		People people2 = new People(18,"zho");
		People people3 = new People(12,"zh");
		People people4 = new People(21,"z");
		list.add(people1);
		list.add(people2);
		list.add(people3);
		list.add(people4);
		for(People people:list) {
			System.out.println(people);
		}
		Collections.sort(list);
System.out.println("--------------------------");		
		for(People people:list) {
			System.out.println(people);
		}
	}
}

你自己改一下比较大小的逻辑 就可以了 另外还有一种方法也可以实现利用comparator

[huntor]

Collections.sort(list, new Comparator<User>(){
public int compare(User u1, User u2){
String p1 = u1.getPercent();
String p2 = u2.getPercent();
if(p1.equals(p2)) return 0;
DecimalFormat formatter = NumberFormat.getPercentInstance();
double d1 = formatter.parse(p1);
double d2 = formatter.parse(p2);
if(d1 > d2) return 1;
return -1;
}
});

[西部流云]

User类需要实现 Compareable接口里面的compareTo方法。
然后根据Collections.sort进行排序就可以了。

[sklyn1984]

double d1 = formatter.parse(p1);
double d2 = formatter.parse(p2);
这里转不了 报错是为啥

[sklyn1984]

double d1 = formatter.parse(p1);
double d2 = formatter.parse(p2);
这里转不了 报错是为啥

[funfenffun]

comparable 或者 comparator
建议用comparator吧，这个比较独立，不用跟User类绑到一起

[sklyn1984]

double d1 = formatter.parse(p1);
double d2 = formatter.parse(p2);
这里转不了 报错是为啥

[sklyn1984]

formatter.parse(p1) 是Number类型

[sklyn1984]

Collections.sort(list, new Comparator<TerminalPerformanceObj>(){
				  public int compare(TerminalPerformanceObj u1, TerminalPerformanceObj u2){
				  String p1 = u1.getMtSuccPercent();;
				  String p2 = u2.getMtSuccPercent();
				  if(p1.equals(p2)) return 0;
				  DecimalFormat formatter = (DecimalFormat) NumberFormat.getPercentInstance();
				  Number d1 = null;
				try {
					d1 = formatter.parse(p1);
				} catch (ParseException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				  Number d2 = null;
				try {
					d2 = formatter.parse(p2);
				} catch (ParseException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				  if(d1.floatValue() > d2.floatValue()) return 1;
				  return -1;
				  }
				  });

我改了一下，但是实际结果却是按从小到大的排序，如何能按从大到小排序呢