java.util.EnumMap.containsKey(Object key) 方法確定如果此映射包含指定鍵的映射關係。

聲明

以下是java.util.EnumMap.containsKey()方法的聲明

public boolean containsKey(Object key)

參數

• key-- 其是否存在於此映射中的鍵

返回值

如果此映射包含指定鍵的映射此方法返回true。

異常

• NA

例子

下麵的示例演示java.util.EnumMap.containsKey()方法的用法。

package com.yiibai;

import java.util.EnumMap;

public class EnumMapDemo {

   // create an enum
   public enum Numbers {

      ONE, TWO, THREE, FOUR, FIVE
   };

   public static void main(String[] args) {
      EnumMap<Numbers, String> map =
              new EnumMap<Numbers, String>(Numbers.class);

      // associate values in map
      map.put(Numbers.ONE, "1");
      map.put(Numbers.TWO, "2");
      map.put(Numbers.THREE, "3");
      map.put(Numbers.FOUR, "4");

      // print the whole map
      System.out.println(map);

      // check if map contains a mapping at specified key
      boolean contains = map.containsKey(Numbers.ONE);

      // print the result
      System.out.println("Numbers.ONE has a mapping:" + contains);

      // check if map contains a mapping at another specified key
      contains = map.containsKey(Numbers.FIVE);

      // print the result
      System.out.println("Numbers.FIVE has a mapping:" + contains);

   }
}

讓我們來編譯和運行上麵的程序，這將產生以下結果：

{ONE=1, TWO=2, THREE=3, FOUR=4}
Numbers.ONE has a mapping:true
Numbers.FIVE has a mapping:false