Java中的 HashMap getOrDefault(key, defaultValue) 方法及示例
Map接口的getOrDefault(Object key, V defaultValue)方法,由HashMap类实现,用于获取指定key映射的值。如果没有使用提供的键映射任何值,则返回默认值。
句法:
default V getOrDefault(Object key, V defaultValue)
参数:此方法接受两个参数:
- key:这是必须获取其值的元素的键。
- defaultValue:如果没有与指定键映射的值,则这是必须返回的默认值。
返回值:此方法返回与指定键映射的值,否则返回默认值。
方案一:
// 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 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
方案二:
// 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 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
参考资料: https: Java/util/HashMap.html#getOrDefault-java.lang.Object-V-