java接口-set

import java.util.HashSet;
import java.util.Objects;
import java.util.Set;

/**
 * 测试set
 * set：无序，不可重复
 */
public class SetTest {
    public static void main(String[] args) {
        test01();
        test02();

    }

    public static void test01(){
        Set s = new HashSet();
        s.add("Hello");
        s.add("world");
        s.add("Hello");//相等的元素不会被加入
        //其他的方法和list一致，因为都是collection接口的子接口
        System.out.println(s);
    }
    //set中不可重复的核心，equals()方法
    public static void test02(){
        Emp e1 = new Emp(1001,"张三");
        Emp e2 = new Emp(1002,"李四");
        Emp e3 = new Emp(1001,"王二狗");

        Set s = new HashSet();
        s.add(e1);
        s.add(e2);
        s.add(e3);
        System.out.println(s);


    }
}
class Emp {
    private int id;
    private String ename;

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Emp emp = (Emp) o;
        return id == emp.id;
    }

    @Override
    public int hashCode() {
        return Objects.hash(id);
    }

    public Emp(int id, String ename) {
        this.id = id;
        this.ename = ename;
    }

    @Override
    public String toString() {
        return "Emp{" +
                "id=" + id +
                ", ename='" + ename + '\'' +
                '}';
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getEname() {
        return ename;
    }

    public void setEname(String ename) {
        this.ename = ename;
    }
}