Java 中的 HashMap getOrDefault(key，defaultValue)方法，示例
原文:https://www . geesforgeks . org/hashmap-getordefaultkey-defaultvalue-method-in-Java-with-examples/
映射接口 的 getOrDefault(Object key，V defaultValue) 方法，由 HashMap 类 实现，用于获取用指定 key 映射的值。如果没有值与提供的键映射，则返回默认值。
语法:
default V getOrDefault(Object key, V defaultValue)
参数:此方法接受两个参数:
- key: is the key of the element whose value must be obtained.
- Default value: is the default value of that must be returned, if there is no value mapped with the specified key.
返回值:此方法返回用指定键映射的值，否则返回默认值。
程序 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);
}
}
输出:
HashMap: {a=100, b=200, c=300, d=400}
Returned Value: 200
程序二:
// 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);
}
}
输出:
HashMap: {a=100, b=200, c=300, d=400}
Returned Value: 500
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