2021-11-17 Java Collections集合工具类

Collections集合工具类，方便集合的操作。

public static void main(String[] args) {
    //ArrayList是线程不安全的
    List list = new ArrayList<>();
    //变成线程安全的
    Collections.synchronizedList(list);
    //排序
    list.add("abbd");
    list.add("dwadwa");
    list.add("avwe");
    list.add("xvsfe");
    Collections.sort(list);
    for (String s:list) {
        System.out.println(s);
    }

   List wuGui2s= new ArrayList<>();
   wuGui2s.add(new WuGui2(123));
   wuGui2s.add(new WuGui2(435));
   wuGui2s.add(new WuGui2(145));
   Collections.sort(wuGui2s);
    for (WuGui2 ww:wuGui2s) {
        System.out.println(ww);
    }
    }
}
class WuGui2 implements Comparable {
    int age;
    public WuGui2(int age) {
        this.age = age;
    }
    @Override
     public int compareTo(WuGui2 o) {
        return this.age-o.age;
    }
    @Override
    public String toString() {
        return "[" +
                "小乌龟龟的age=" + age +
                ']';
    }

对Set集合进行排序，先转成list集合再排序，代码如下：

public static void main(String[] args) {
   Set set = new HashSet<>();
   set.add("123");
   set.add("sfd");
   set.add("f53f");
   List mylist = new ArrayList<>(set);
   Collections.sort(mylist);
    for (String s:mylist) {
        System.out.println(s);
    }
}