IdentityHashMap类putAll()方法 (IdentityHashMap 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 entry (key-value pairs) that exists from the given map (m) and paste it into this IdentityHashMap.

  putAll()方法用于复制给定映射(m)中存在的所有条目(键值对)，并将其粘贴到此IdentityHashMap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 key-value pairs.

  在复制键值对时， putAll()方法可能会引发异常。

  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 object that contains key-value pairs to be copied from.

  Map m –表示Map对象，其中包含要从中复制的键/值对。

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 IdentityHashMap
import java.util.*;
public class PutAllOfIdentityHashMap {public static void main(String[] args) {// Instantiates a IdentityHashMap object
Map < Integer, String > map = new IdentityHashMap < Integer, String > ();
Map < Integer, String > put_map = new IdentityHashMap < Integer, String > ();
// By using put() method is to add
// key-value pairs in a IdentityHashMap
map.put(10, "C");
map.put(20, "C++");
map.put(50, "JAVA");
map.put(40, "PHP");
map.put(30, "SFDC");
// Display IdentityHashMap
System.out.println("IdentityHashMap: " + 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 IdentityHashMap
System.out.print("put_map.putAll(map): " + put_map);
}
}

Output

输出量

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

翻译自: https://www.includehelp.com/java/identityhashmap-putall-method-with-example.aspx