Java中的 SimpleBindings containsKey() 方法及示例

如果支持此 SimpleBindings 对象的此映射包含指定键的映射，则SimpleBindings 类的containsKey()方法用于返回 true。如果 SimpleBindings 对象包含此键，则该方法返回 true，否则返回 false。

句法：

public boolean containsKey(Object key)

参数：此方法仅接受一个参数键，该键是要在此映射中测试其存在的键。

返回值：如果此映射包含指定键的映射，则此方法返回 true。

异常：此方法抛出以下异常：

• NullPointerException : 如果键为空
• ClassCastException : 如果键不是字符串
• IllegalArgumentException : 如果键为空字符串

说明 containsKey() 方法工作的Java程序：

方案一：

// Java program to demonstrate containsKey() method
  
import javax.script.SimpleBindings;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create simpleBindings object
        SimpleBindings bindings = new SimpleBindings();
  
        // add some keys with values
        bindings.put("key1", "value1");
        bindings.put("key2", "value2");
        bindings.put("key3", "value3");
  
        // check key2 is exists in bindings or not
        boolean isKey2Exist = bindings.containsKey("key2");
  
        // print
        System.out.println("Key2 exits:" + isKey2Exist);
    }
}

输出：

Key2 exits:true

方案二：

// Java program to demonstrate containsKey() method
  
import javax.script.SimpleBindings;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // create simpleBindings object
        SimpleBindings asiaTeamList
            = new SimpleBindings();
  
        // add team in asiaTeamList
        asiaTeamList.put("team1", "India");
        asiaTeamList.put("team2", "Sri Lanka");
        asiaTeamList.put("team3", "Pakistan");
        asiaTeamList.put("team4", "Bangladesh");
  
        // check England exists in bindings or not
        boolean isKey2Exist
            = asiaTeamList.containsKey("England");
  
        // print
        System.out.println("England exits in Asia Team:"
                           + isKey2Exist);
    }
}

输出：

England exits in Asia Team:false

参考资料： https://docs.oracle.com/javase/10/docs/api/javax/script/SimpleBindings.html#containsKey(Java.lang.Object)