Java中的equals()方法及其示例

java.util.Set 类的 equals() 方法用于验证一个对象与一个Set集合的相等性并进行比较，如果两个集合的元素数量相等且包含相同的元素，则该方法返回true。

语法:

public boolean equals(Object o)

参数: 该方法将对象o作为参数以与此集合进行比较。

返回值: 如果指定的对象与此集合相等，则该方法返回true。

以下是说明 equals() 方法的示例。

示例1:

// Java program to demonstrate equals() method of Set
   
import java.util.*;
   
public class GFG {
    public static void main(String[] argv)
    {
   
        // Creating object of Set
        Set<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 Set: "
                            + arrset1);
   
        // Creating another object of Set
        Set<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 Set: "
                            + arrset2);
   
        // comparing first Set to another
        // using equals() method
        boolean value = arrset1.equals(arrset2);
   
        // print the value
        System.out.println("Are both set equal? "
                            + value);
    }
}

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

示例2：

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

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

引用 : https://docs.oracle.com/javase/7/docs/api/java/util/Set.html#equals(java.lang.Object)