常用API-Hashset、迭代器、重写equals

 

import java.util.HashSet;
import java.util.Iterator;

public class fuxi4_hashset
{
    public static void main(String[] args)
    {
        /************************* 容器间Hashset、迭代器 *************************************************/
        HashSet<Student> stu = new HashSet<Student>();//去重复，按容器自己的顺序排列
        Student s1 = new Student("tom", 25);
        Student s2 = new Student("jerry", 23);
        Student s3 = new Student("jerry", 23);
        Student s4 = new Student("tom", 22);
        stu.add(s1);
        stu.add(s2);
        stu.add(s3);
        stu.add(s4);

        Iterator itr = stu.iterator();// 创建迭代器
        while(itr.hasNext())
        {
            Student str = (Student) itr.next();
            System.out.println(str);
        }
    }

    /************************* 重写equals方法 *************************************************/
    /**
     * public boolean equals(Object obj)
    {
        System.out.println("asdf");
        if (obj instanceof Student)
        {
            Student s = (Student) obj;

            if (this.name.equals(s.name) && this.age == s.age)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
        else
        {
            System.out.println("null");
            return false;
        }
    }
     */
}


class Student
{
    String name;
    int age;
    public Student(String name, int age)
    {
        this.name = name;
        this.age = age;
    }
    @Override
    public String toString()
    {
        return "Student [name=" + name + ", age=" + age + "]";
    }
    @Override
    public int hashCode()
    {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }
    @Override
    public boolean equals(Object obj)
    {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Student other = (Student) obj;
        if (age != other.age)
            return false;
        if (name == null)
        {
            if (other.name != null)
                return false;
        }
        else if (!name.equals(other.name))
            return false;
        return true;
    }
}

 

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