Java EnumMap containsKey() 方法

如果此映射包含指定键的映射，则 java.util.EnumMap.containsKey() 方法返回 true。

语法

public boolean containsKey(Object key)

参数

返回值

如果该映射包含指定键的映射，则返回 true。

异常

示例:

在下面的示例中，java.util.EnumMap .containsKey() 方法用于检查给定 EnumMap 中是否存在指定键。

import java.util.*;

public class MyClass {
  
  //创建一个枚举
  public enum weekday{
    SUN, MON, TUE, WED, THU, FRI, SAT
  }

  public static void main(String[] args) {
    //创建一个EnumMap
    EnumMap<weekday,Integer> MyMap = 
        new EnumMap<weekday,Integer>(weekday.class);

    //关联map中的值
    MyMap.put(weekday.MON, 1);
    MyMap.put(weekday.TUE, 2);
    MyMap.put(weekday.WED, 3);
    MyMap.put(weekday.THU, 4);
    MyMap.put(weekday.FRI, 5);

    //打印EnumMap
    System.out.println("MyMap contains: " + MyMap);   

    //检查SUN密钥是否存在
    System.out.print("Does MyMap contain SUN key? - ");  
    System.out.println(MyMap.containsKey(weekday.SUN));  

    //检查 FRI 密钥是否存在
    System.out.print("Does MyMap contain FRI key? - ");  
    System.out.println(MyMap.containsKey(weekday.FRI));  
  }
}

上述代码的输出将是:

MyMap contains: {MON=1, TUE=2, WED=3, THU=4, FRI=5}
Does MyMap contain SUN key? - false
Does MyMap contain FRI key? - true