Java 中的 Map equals()方法，示例

原文:https://www . geesforgeks . org/map-equals-method-in-Java-with-examples/

java 中的 java.util.Map.equals()方法用于检查两个映射之间的相等性。它验证作为参数传递的一个映射的元素是否等于这个映射的元素。

语法:

boolean equals(object obj)

参数:该方法接受该地图类型的一个参数对象，并引用要用该地图检查其相等性的地图。

返回值:如果两个对象映射相等，则方法返回真，否则返回假。

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));
    }
}

Output:

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

程序 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, "4");
        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, "Geek");
        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));
    }
}

Output:

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

参考:https://docs . Oracle . com/javase/7/docs/API/Java/util/map . html # equals(Java . lang . object)

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