java相关：List对象去重和按照某个字段排序的实现方法
发布于 -6-8|
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下面小妖就为大家带来一篇List对象去重和按照某个字段排序的实现方法。小妖觉得挺不错的，现在就分享给大家，也给大家做个参考。一起跟随小妖过来看看吧
1、List去重People类
```java
public class People {
private int id;
private String name;
private Date createDate;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getCreateDate() {
return createDate;
}
public void setCreateDate(Date createDate) {
this.createDate = createDate;
}
}
```
main方法
```java
public static void main(String[] args) throws Exception{
List list = new ArrayList();
People p1 = new People();
p1.setId(1);
p1.setName("赵");
list.add(p1);
People p2 = new People();
p2.setId(2);
p2.setName("钱");
list.add(p2);
People p3 = new People();
p3.setId(3);
p3.setName("孙");
list.add(p3);
People p4 = new People();
p4.setId(4);
p4.setName("李");
list.add(p4);
People p5 = new People();
p5.setId(5);
p5.setName("周");
list.add(p5);
list.add(p1);
for(People p : list){
System.out.println(p);
}
System.out.println("==========================");
Set set = new HashSet(list);
list.clear();
list.addAll(new ArrayList(set));
for(People p : list){
System.out.println(p);
}
}
```
2、List按照日期字段排序
自定义Comparator
```java
public class MyComparator implements Comparator {
@Override
public int compare(People p1, People p2) {
return p1.getCreateDate().compareTo(p2.getCreateDate());
}
}
```
main方法
```java
public static void main(String[] args) throws Exception{
List list = new ArrayList();
People p1 = new People();
p1.setId(1);
p1.setName("赵");
p1.setCreateDate(new Date(new Date().getTime() + 1000));
list.add(p1);
People p2 = new People();
p2.setId(2);
p2.setName("钱");
p2.setCreateDate(new Date(new Date().getTime() + 8000));
list.add(p2);
People p3 = new People();
p3.setId(3);
p3.setName("孙");
p3.setCreateDate(new Date(new Date().getTime() + 7000));
list.add(p3);
People p4 = new People();
p4.setId(4);
p4.setName("李");
p4.setCreateDate(new Date(new Date().getTime() + 5000));
list.add(p4);
People p5 = new People();
p5.setId(5);
p5.setName("周");
p5.setCreateDate(new Date(new Date().getTime() + 6000));
list.add(p5);
for(People p : list){
System.out.println(p.getId());
}
//1,2,3,4,5
System.out.println("=======================");
Collections.sort(list, new MyComparator());
//1,4,5,3,2
for(People p : list){
System.out.println(p.getId());
}
}
```
