Java HashSet equals()方法及示例

java.util.HashSet 类的 equals() 方法用于验证一个对象与一个HashSet的平等性，并对它们进行比较。只有当两个HashSet包含相同的元素时，该列表才会返回真，而不考虑顺序。

语法

public boolean equals(Object o)

参数： 该方法以对象o为参数，与这个集合进行平等比较。

返回值： 如果指定的对象与这个集合相等，该方法返回真。

下面是说明 equals() 方法的例子。

例1 :

// Java program to demonstrate equals()
// method of HashSet
  
import java.util.*;
  
public class GFG {
    public static void main(String[] argv)
    {
  
        // Creating object of HashSet<String>
        HashSet<String>
            arrset1 = new HashSet<String>();
  
        // Populating arrset1
        arrset1.add("A");
        arrset1.add("B");
        arrset1.add("C");
        arrset1.add("D");
        arrset1.add("E");
  
        // print arrset1
        System.out.println("First HashSet: "
                           + arrset1);
  
        // Creating another object of HashSet<String>
        HashSet<String>
            arrset2 = new HashSet<String>();
  
        // Populating arrset2
        arrset2.add("A");
        arrset2.add("B");
        arrset2.add("C");
        arrset2.add("D");
        arrset2.add("E");
  
        // print arrset2
        System.out.println("Second HashSet: "
                           + arrset2);
  
        // comparing first HashSet to another
        // using equals() method
        boolean value
            = arrset1.equals(arrset2);
  
        // print the value
        System.out.println("Are both set equal: "
                           + value);
    }
}

输出:

First HashSet: [A, B, C, D, E]
Second HashSet: [A, B, C, D, E]
Are both set equal: true

例2 :

// Java program to demonstrate equals()
// method of HashSet
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv)
    {
  
        // Creating object of HashSet
        HashSet<Integer>
            arrset1 = new HashSet<Integer>();
  
        // Populating arrset1
        arrset1.add(10);
        arrset1.add(20);
        arrset1.add(30);
        arrset1.add(40);
        arrset1.add(50);
  
        // print arrset1
        System.out.println("First HashSet: "
                           + arrset1);
  
        // Creating another object of HashSet
        HashSet<Integer>
            arrset2 = new HashSet<Integer>();
  
        // Populating arrset2
        arrset2.add(10);
        arrset2.add(20);
        arrset2.add(30);
  
        // print arrset2
        System.out.println("Second HashSet: "
                           + arrset2);
  
        // comparing first HashSet to another
        // using equals() method
        boolean value = arrset1.equals(arrset2);
  
        // print the value
        System.out.println("Are both set equal: "
                           + value);
    }
}

输出:

First HashSet: [50, 20, 40, 10, 30]
Second HashSet: [20, 10, 30]
Are both set equal: false