Java中的属性 clear() 方法和示例

Java.util.Properties.clear()方法用于从此 Properties 实例中删除所有元素。使用 clear() 方法只会清除属性中的所有元素，不会删除属性。换句话说，我们可以说 clear() 方法仅用于清空现有的属性。

句法：

public void clear()

参数：该方法不带任何参数

返回值：该函数不返回任何值。

下面的程序说明了Java.util.Properties.clear() 方法。

示例 1：

// Java code illustrating clear() method
  
import java.util.*;
  
class PropertiesDemo {
    public static void main(String arg[])
    {
        Properties gfg = new Properties();
        Set URL;
        String str;
  
        gfg.put("ide",
                "ide.geeksforgeeks.org");
        gfg.put("contribute",
                "write.geeksforgeeks.org");
        gfg.put("quiz",
                "quiz.geeksforgeeks.org");
  
        // checking what's in table
        System.out.println("Current Properties: "
                           + gfg.toString());
  
        System.out.println("\nClearing the Properties");
        gfg.clear();
  
        // checking what's in table now
        System.out.println("New Properties: "
                           + gfg.toString());
    }
}

输出：

Current Properties: {contribute=write.geeksforgeeks.org, quiz=quiz.geeksforgeeks.org, ide=ide.geeksforgeeks.org}

Clearing the Properties
New Properties: {}

示例 2：

// Java code illustrating clear() method
  
import java.util.*;
  
class PropertiesDemo {
    public static void main(String arg[])
    {
        Properties gfg = new Properties();
        Set URL;
        String str;
  
        gfg.put(1, "Geeks");
        gfg.put(2, "GeeksforGeeks");
        gfg.put(3, "Geek");
  
        // checking what's in table
        System.out.println("Current Properties: "
                           + gfg.toString());
  
        System.out.println("\nClearing the Properties");
        gfg.clear();
  
        // checking what's in table now
        System.out.println("New Properties: "
                           + gfg.toString());
    }
}

输出：

Current Properties: {3=Geek, 2=GeeksforGeeks, 1=Geeks}

Clearing the Properties
New Properties: {}

参考： https://docs.oracle.com/javase/9/docs/api/ Java/util/Properties.html#clear–