Java Map equals()方法及实例

Java中的java.util.Map.equals()方法是用来检查两个地图之间是否相等。它验证了作为参数传递的一个地图的元素是否等于这个地图的元素。

语法

boolean equals(object obj)

参数： 该方法接受一个该地图类型的参数obj，并指的是要与该地图进行平等检查的地图。

返回值： 如果obj和Map的平等性都成立，该方法就会返回true，否则就会返回false。

下面的程序说明了java.util.Map.equals()方法：

程序1 :

// Java code to illustrate the equals() method
import java.util.*;
  
public class Map_Demo {
    public static void main(String[] args)
    {
        // Creating an empty Map
        Map<Integer, String> map1 = new HashMap<Integer, String>();
        Map<Integer, String> map2 = new HashMap<Integer, String>();
  
        // Mapping string values to int keys
        map1.put(10, "Geeks");
        map1.put(15, "4");
        map1.put(20, "Geeks");
        map1.put(25, "Welcomes");
        map1.put(30, "You");
  
        // Mapping string values to int keys
        map2.put(10, "Geeks");
        map2.put(15, "4");
        map2.put(20, "Geeks");
        map2.put(25, "Welcomes");
        map2.put(30, "You");
  
        // Displaying the Map1
        System.out.println("First Map: "
                           + map1);
  
        // Displaying the Map2
        System.out.println("Second Map: "
                           + map2);
  
        // Checking the equality
        System.out.println("Equality: " + map1.equals(map2));
    }
}

输出。

First Map: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
Second Map: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
Equality: true

示例2 。

// Java code to illustrate the equals() method
import java.util.*;
  
public class Map_Demo {
    public static void main(String[] args)
    {
        // Creating an empty Map
        Map<Integer, String> map1 = new HashMap<Integer, String>();
        Map<Integer, String> map2 = new HashMap<Integer, String>();
  
        // Mapping string values to int keys for map1
        map1.put(10, "Geeks");
        map1.put(15, "four");
        map1.put(20, "Geeks");
        map1.put(25, "Welcomes");
        map1.put(30, "You");
  
        // Mapping string values to int keys for map2
        map2.put(10, "Geeks");
        map2.put(15, "4");
        map2.put(20, "Geeks");
        map2.put(25, "Welcomes");
        map2.put(30, "You");
  
        // Displaying the map 1
        System.out.println("First Map: " + map1);
  
        // Displaying the map 2
        System.out.println("Second Map: " + map2);
  
        // Displaying the equality
        System.out.println("Equality: " + map1.equals(map2));
    }
}

输出。

First Map: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=four}
Second Map: {20=Geek, 25=Welcomes, 10=Geeks, 30=You, 15=4}
Equality: false

参考资料 : https://docs.oracle.com/javase/7/docs/api/java/util/Map.html#equals(java.lang.Object)