The getOrDefault(Object key, V defaultValue) method of Map interface, implemented by HashMap class is used to get the value mapped with specified key. If no value is mapped with the provided key then the default value is returned.

Syntax:

default V getOrDefault(Object key, V defaultValue)

Parameters: This method accepts two parameters:

key: which is the key of the element whose value has to be obtained.
defaultValue: which is the default value that has to be returned, if no value is mapped with the specified key.

Return Value: This method returns value mapped with the specified key, otherwise default value is returned.

解釋

意思就是當(dāng)Map集合中有這個key時(shí)，就使用這個key值，如果沒有就使用默認(rèn)值defaultValue

實(shí)例

Program 1：

// Java program to demonstrate?
// getOrDefault(Object key, V defaultValue) method?

import java.util.*;?

public class GFG {?

?? ?// Main method?
?? ?public static void main(String[] args)?
?? ?{?

?? ??? ?// Create a HashMap and add some values?
?? ??? ?HashMap<String, Integer> map?
?? ??? ??? ?= new HashMap<>();?
?? ??? ?map.put("a", 100);?
?? ??? ?map.put("b", 200);?
?? ??? ?map.put("c", 300);?
?? ??? ?map.put("d", 400);?

?? ??? ?// print map details?
?? ??? ?System.out.println("HashMap: "
?? ??? ??? ??? ??? ??? ?+ map.toString());?

?? ??? ?// provide key whose value has to be obtained?
?? ??? ?// and default value for the key. Store the?
?? ??? ?// return value in k?
?? ??? ?int k = map.getOrDefault("b", 500);?

?? ??? ?// print the value of k returned by?
?? ??? ?// getOrDefault(Object key, V defaultValue) method?
?? ??? ?System.out.println("Returned Value: " + k);?
?? ?}?
}?

Output：

HashMap: {a=100, b=200, c=300, d=400}
Returned Value: 200

Program 2：

// Java program to demonstrate?
// getOrDefault(Object key, V defaultValue) method?

import java.util.*;?

public class GFG {?

?? ?// Main method?
?? ?public static void main(String[] args)?
?? ?{?

?? ??? ?// Create a HashMap and add some values?
?? ??? ?HashMap<String, Integer> map?
?? ??? ??? ?= new HashMap<>();?
?? ??? ?map.put("a", 100);?
?? ??? ?map.put("b", 200);?
?? ??? ?map.put("c", 300);?
?? ??? ?map.put("d", 400);?

?? ??? ?// print map details?
?? ??? ?System.out.println("HashMap: "
?? ??? ??? ??? ??? ??? ?+ map.toString());?

?? ??? ?// provide key whose value has to be obtained?
?? ??? ?// and default value for the key. Store the?
?? ??? ?// return value in k?
?? ??? ?int k = map.getOrDefault("y", 500);?

?? ??? ?// print the value of k returned by?
?? ??? ?// getOrDefault(Object key, V defaultValue) method?
?? ??? ?System.out.println("Returned Value: " + k);?
?? ?}?
}?

Output: