字典的put()方法用于在字典中插入映射。这意味着可以将特定键及其值映射到特定字典中。

用法:

DICTIONARY.put(key, value)

参数：该方法有两个参数，都属于Dictionary的Object类型。

key:这是指需要插入字典以进行映射的关键元素。

value:这是指以上键将映射到的值。

返回值：该方法返回键所映射到的值。如果键未映射到任何值，则返回NULL。

以下程序用于说明java.util.Dictionary.put()方法的用法：

示例1:

// Java code to illustrate the put() method

import java.util.*;

public class Dictionary_Demo {

public static void main(String[] args)

{

// Creating an empty Dictionary

Dictionary dict

= new Hashtable();

// Inserting values into the Dictionary

dict.put(10, "Geeks");

dict.put(15, "4");

dict.put(20, "Geeks");

dict.put(25, "Welcomes");

dict.put(30, "You");

// Displaying the Dictionary

System.out.println("Initial Dictionary is: " + dict);

// Inserting existing key along with new value

String returned_value = (String)dict.put(20, "All");

// Verifying the returned value

System.out.println("Returned value is: " + returned_value);

// Displaying the new table

System.out.println("New Dictionary is: " + dict);

}

}

输出：

Initial Dictionary is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes}

Returned value is: Geeks

New Dictionary is: {10=Geeks, 20=All, 30=You, 15=4, 25=Welcomes}

示例2:

// Java code to illustrate the put() method

import java.util.*;

public class Dictionary_Demo {

public static void main(String[] args)

{

// Creating an empty Dictionary

Dictionary dict

= new Hashtable();

// Inserting values into the Dictionary

dict.put(10, "Geeks");

dict.put(15, "4");

dict.put(20, "Geeks");

dict.put(25, "Welcomes");

dict.put(30, "You");

// Displaying the Dictionary

System.out.println("Initial Dictionary is: " + dict);

// Inserting existing key along with new value

String returned_value = (String)dict.put(50, "All");

// Verifying the returned value

System.out.println("Returned value is: " + returned_value);

// Displaying the new table

System.out.println("New Dictionary is: " + dict);

}

}

输出：

Initial Dictionary is: {10=Geeks, 20=Geeks, 30=You, 15=4, 25=Welcomes}

Returned value is: null

New Dictionary is: {10=Geeks, 20=Geeks, 30=You, 50=All, 15=4, 25=Welcomes}