Java实现对List中的对象按某个字段进行排序

最新推荐文章于 2024-12-21 20:23:09 发布

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#java #快速排序 #接口 #lambda #后端

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本文介绍了一种使用Java对Logs实体类列表按times字段进行排序的方法，展示了如何通过实现Comparable接口和使用Collections.sort方法结合自定义Comparator来实现降序和升序排序。

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public class Logs implements Serializable, Comparable<Logs> {
 
    private String id;
    private String username;
    private String contents;
    private String consequence;
    private String ip;
    private Long times;
 
    @Override
    public int compareTo(Logs o) {
        return 0;
    }
 
}
解析: Logs实体,要继承Comparable<T>接口, 然后再实现一个public int compareTo(Logs o) 方法.

现在,我要对List<Logs> 中的数据按 times 字段进行排序


    @Test
    public void testMath(){
        List<Logs> list = new ArrayList<Logs>();
        list.add(new Logs("1","chen", "djifand", "jdifa", "jdfid", 49L));
        list.add(new Logs("134","ce", "cae", "jdifa", "jdfid", 123L));
        list.add(new Logs("3","cet", "djifand", "jdifa", "jdfid", 99L));
        list.add(new Logs("4","egge", "djifand", "jdifa", "jdfid", 111L));
        list.add(new Logs("15","chen", "djifand", "jdifa", "jdfid", 59L));
        list.add(new Logs("6","chen2", "cae", "jdifa", "jdfid", 123L));
        list.add(new Logs("87","cet", "djifand", "jdifa", "jdfid", 213L));
        list.add(new Logs("8","egge", "djifand", "jdifa", "jdfid", 201L));
        list.add(new Logs("9","egge2", "djifand", "jdifa", "jdfid", 269L));
        list.add(new Logs("10","ce", "cae", "jdifa", "jdfid", 121L));
        list.add(new Logs("11","chen3", "djifand", "jdifa", "jdfid", 1123L));
        list.add(new Logs("5","cet2", "djifand", "jdifa", "jdfid", 12L));
 
        System.out.println("---- 排序前的输出  ----- ");
        for (Logs logs : list) {
            System.out.println("数据: "+logs);
        }
        System.out.println("---- 排序后的结果  ----- ");
        List<Logs> search = search(list);
 
        for (Logs logs : search) {
            System.out.println("-->"+logs);
        }
 
    }
 
 
     // 方式1: 降序排列
     public List<Logs> search(List<Logs> logsList){
        Collections.sort(logsList, new Comparator<Logs>() {
            @Override
            public int compare(Logs o1, Logs o2) {
                if ((o1.getTimes() > o2.getTimes())){
                    return -1;
                }
                if (o1.getTimes() == o2.getTimes()){
                    return 0;
                }
                return 1;
            }
        });
        return logsList;
    }
 
     // 方式2: 升序排列
     public List<Logs> search(List<Logs> logsList){
        Collections.sort(logsList, new Comparator<Logs>() {
            @Override
            public int compare(Logs o1, Logs o2) {
                if ((o1.getTimes() > o2.getTimes())){
                    return 1;
                }
                if (o1.getTimes() == o2.getTimes()){
                    return 0;
                }
                return -1;
            }
        });
        return logsList;
    }
    // 方式3: 降序排列 
    public List<Logs> search(List<Logs> logsList){
        Collections.sort(logsList, new Comparator<Logs>() {
            @Override
            public int compare(Logs o1, Logs o2) {
                return -o1.getTimes().compareTo(o2.getTimes());
            }
        });
        return logsList;
    }
 
    // 方式4: 升序排列
    public List<Logs> search(List<Logs> logsList){
        Collections.sort(logsList, new Comparator<Logs>() {
            @Override
            public int compare(Logs o1, Logs o2) {
                return o1.getTimes().compareTo(o2.getTimes());
            }
        });
        return logsList;
    }