List对象去重和按照某个字段排序的实现方法_Java教程

List对象去重和按照某个字段排序的实现方法

2020-10-20 10:24脚本之家 Java教程

下面小编就为大家带来一篇List对象去重和按照某个字段排序的实现方法。小编觉得挺不错的，现在就分享给大家，也给大家做个参考。一起跟随小编过来看看吧

1、List<Object>去重

People类

				?

									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

				?

									public static void main(String[] args) throws Exception{ 

									    List<People> list = new ArrayList<People>(); 

									    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<People> set = new HashSet<People>(list); 

									    list.clear(); 

									    list.addAll(new ArrayList<People>(set)); 

									    for(People p : list){ 

									      System.out.println(p); 

									    } 

									  }

2、List<Object>按照日期字段排序

自定义Comparator

				?

									public class MyComparator implements Comparator<People> { 

									  @Override

									  public int compare(People p1, People p2) { 

									    return p1.getCreateDate().compareTo(p2.getCreateDate()); 

									  } 

									}

main方法

				?

									public static void main(String[] args) throws Exception{ 

									    List<People> list = new ArrayList<People>(); 

									    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()); 

									    } 

									  }