Java中的Set集合简单汇总解析

public class Example01 {
  public static void main(String[] args) {
    HashSet set = new HashSet();
    set.add("老大");
    set.add("老二");
    set.add("老三");
    set.add("老二");
    Iterator it = set.iterator();
    while(it.hasNext()) {
      Object obj = it.next();
      System.out.println(obj);
    }
  }
}

class Student{
  String id;
  String name;
  public Student(String id, String name) {
    super();
    this.id = id;
    this.name = name;
  }
  @Override
  public String toString() {
    return id+":"+name;
  }
  @Override
  public int hashCode() {
    return id.hashCode();    //返回id属性的哈希值
  }
  @Override
  public boolean equals(Object obj) {
    if(this == obj) {    //判断是否是同一个对象
      return true;    //如果是,直接返回true
    }
    if(!(obj instanceof Student)) {    //判断对象是为Student类型
      return false;    //如果对象不是Student类型返回false
    }
    Student stu = (Student) obj;    //将对象强转为Student类型
    boolean b = this.id.equals(stu.id);    //判断id值是否相同
    return b;  //返回判断结果
  }
}
public class Example02 {
  public static void main(String[] args) {
    HashSet set = new HashSet();
    set.add(new Student("1", "老王"));
    set.add(new Student("2", "老三"));
    set.add(new Student("2", "老三"));
    System.out.println(set);
  }
}