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 <strong style="color:transparent">来源gao@daima#com搞(%代@#码@网</strong>getCreateDate() { return createDate; } public void setCreateDate(Date createDate) { this.createDate = createDate; } }
main方法
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
public class MyComparator implements Comparator { @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 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()); } }
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