Java 中的 HashSet equals()方法，示例

原文:https://www . geesforgeks . org/hashset-equals-method-in-Java-with-example/

java.util.HashSet 类的 equals() 方法用于验证对象与 HashSet 的相等性并进行比较。只有当两个 HashSet 包含相同的元素时，列表才返回 true，与顺序无关。

语法:

public boolean equals(Object o)

参数:该方法以的对象为参数，与该集合进行相等性比较。

返回值:如果指定的对象等于这个集合，这个方法返回真。

以下是说明等于()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);
    }
}

Output:

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);
    }
}

Output:

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

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