Usage of put method in java

The put method in Java is used to add or update key-value pairs in Map. It adds the specified key and value to the Map, or updates its corresponding value if the key already exists.

Usage of put method in Java

In Java, put method is used to add to Map data structure Or update key-value pairs. Map is an associative array where each key corresponds to a value.

Usage

put(key, value) method adds the specified key and value to the Map. If the key already exists in the Map, the value corresponding to the key will be updated.

Parameters

• key: The key to be added to the Map.
• value: The value to be associated with this key.

Return value

If the key already exists in the Map, the method returns the value previously associated with the key. Otherwise, the method returns null.

Example

Map<String, String> names = new HashMap<>();
names.put("John", "Doe"); // 添加键值对
names.put("John", "Smith"); // 更新键值对

Notes

##Keys and values ​​can be of any object type.
• If the key does not exist, the method will create the key and value and add them to the Map.
• If the key exists, the method only updates the value and does not change the key.
• If the value is
• null, the method will remove the key from the Map.

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