hashmap示例

HashMap类的putAll()方法 (HashMap Class putAll() method)

• putAll() method is available in java.util package.

  putAll()方法在java.util包中可用。

• putAll() method is used to copy all of the key-value pairs that exist from the given map and paste it to this HashMap.

  putAll()方法用于复制给定映射中存在的所有键值对，并将其粘贴到此HashMap中。

• putAll() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.

  putAll()方法是一种非静态方法，只能通过类对象访问，如果尝试使用类名称访问该方法，则会收到错误消息。

• putAll() method may throw an exception at the time of copying mappings.

  putAll()方法在复制映射时可能会引发异常。

  NullPointerException: This exception may throw when the given parameter is null exists.

  NullPointerException ：当给定参数为null时，可能引发此异常。

Syntax:

句法：

public void putAll(Map m);

Parameter(s):

参数：

• Map m – represents the map that contains mappings to be copied.

  映射m –表示包含要复制的映射的映射。

Return value:

返回值：

The return type of the method is void, it returns nothing.

该方法的返回类型为void ，不返回任何内容。

Example:

例：

// Java program to demonstrate the example // of void putAll(Map m) method of HashMap import java.util.*;public class PutAllOfHashMap {
       public static void main(String[] args) {
           // Instantiates a HashMap object        Map < Integer, String > map = new HashMap < Integer, String > ();        Map < Integer, String > put_map = new HashMap < Integer, String > ();        // By using put() method is to add        // key-value pairs in a HashMap        map.put(10, "C");        map.put(20, "C++");        map.put(50, "JAVA");        map.put(40, "PHP");        map.put(30, "SFDC");        // Display HashMap        System.out.println("HashMap: " + map);        // By using putAll() method is to        // copy all of the elements of the given        // object and paste it in an another object        put_map.putAll(map);        // Display put_map HashMap        System.out.print("put_map.putAll(map): " + put_map);    }}

Output

输出量

HashMap: {50=JAVA, 20=C++, 40=PHP, 10=C, 30=SFDC}put_map.putAll(map): {40=PHP, 50=JAVA, 10=C, 20=C++, 30=SFDC}

翻译自:

hashmap示例