Java中的 SimpleBindings remove() 方法及示例

SimpleBindings 类的remove()方法用于从此 SimpleBindings 对象中删除此键的映射（如果存在）。此方法返回与指定键关联的先前值，如果键没有映射，则返回 null。
句法：

public Object remove(Object key)

参数：此方法接受一个参数键，该键是要从映射中删除其映射的键。
返回值：此方法返回与指定键关联的先前值，如果键没有映射，则返回 null。
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。

以下是说明 remove() 方法工作的程序：
示例 1：

Java

// Java programs to Illustrate
// the working of remove() method
 
import javax.script.SimpleBindings;
 
public class GFG {
    public static void main(String[] args)
    {
 
        // create simpleBindings object
        SimpleBindings bindings = new SimpleBindings();
 
        // add key value pair using remove()
        bindings.put("key1", "value1");
        bindings.put("key2", "value2");
        bindings.put("key3", "value3");
 
        // print before removing key1 and key2
        System.out.println("before removing key1 and key2");
        System.out.println("Key1: " + bindings.get("key1"));
        System.out.println("Key2: " + bindings.get("key2"));
        System.out.println("Key3: " + bindings.get("key3"));
 
        // remove key1 and key2
        bindings.remove("key1");
        bindings.remove("key2");
 
        // print after removing key1 and key2
        System.out.println("after removing key1 and key2");
        System.out.println("Key1: " + bindings.get("key1"));
        System.out.println("Key2: " + bindings.get("key2"));
        System.out.println("Key3: " + bindings.get("key3"));
    }
}

输出：

before removing key1 and key2
Key1: value1
Key2: value2
Key3: value3
after removing key1 and key2
Key1: null
Key2: null
Key3: value3

示例 2：

Java

// Java programs to Illustrate
// the working of remove() 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 using remove()
        asiaTeamList.put("team1", "India");
        asiaTeamList.put("team2", "Sri Lanka");
        asiaTeamList.put("team3", "Pakistan");
        asiaTeamList.put("team4", "Bangladesh");
 
        // print before removing
        System.out.println("before removing team3 and team4");
        System.out.println("Team1: " + asiaTeamList.get("team1"));
        System.out.println("Team2: " + asiaTeamList.get("team2"));
        System.out.println("Team3: " + asiaTeamList.get("team3"));
        System.out.println("Team4: " + asiaTeamList.get("team4"));
 
        // remove team3 and team4
        asiaTeamList.remove("team3");
        asiaTeamList.remove("team4");
 
        // print before removing key1 and key2
        System.out.println("after removing team3 and team4");
        System.out.println("Team1: " + asiaTeamList.get("team1"));
        System.out.println("Team2: " + asiaTeamList.get("team2"));
        System.out.println("Team3: " + asiaTeamList.get("team3"));
        System.out.println("Team4: " + asiaTeamList.get("team4"));
    }
}

输出：

before removing team3 and team4
Team1: India
Team2: Sri Lanka
Team3: Pakistan
Team4: Bangladesh
after removing team3 and team4
Team1: India
Team2: Sri Lanka
Team3: null
Team4: null

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