Java Properties keySet()用法及代码示例

Properties类的keySet()方法用于从Properties中包含的关键元素中创建一个集合。它本质上返回键的集合视图，或者我们可以创建一个新集合并将键元素存储在其中。

用法:

public Set keySet()

参数：此方法不接受任何参数

返回值：此方法返回此Properties对象中包含的键的Set视图。

下面的程序显示int keySet()方法的实现。

示例1:

// Java code to show the implementation of 
// keySet() method 
  
import java.util.*; 
public class GfG { 
  
    // Main method 
    public static void main(String[] args) 
    { 
  
        // Create a properties and add some values 
        Properties properties = new Properties(); 
        properties.put("Pen", 10); 
        properties.put("Book", 500); 
        properties.put("Clothes", 400); 
        properties.put("Mobile", 5000); 
  
        // Print Properties details 
        System.out.println("Properties: "
                           + properties.toString()); 
  
        System.out.println("keySet: "
                           + properties.keySet()); 
    } 
}

输出：

Properties: {Book=500, Mobile=5000, Pen=10, Clothes=400}
keySet: [Book, Mobile, Pen, Clothes]

示例2:

// Java program to demonstrate 
// keySet() method. 
  
import java.util.*; 
  
public class GFG { 
  
    // Main method 
    public static void main(String[] args) 
    { 
  
        // Create a properties and add some values 
        Properties properties = new Properties(); 
  
        // Inserting elements into the properties 
        properties.put("Geeks", 10); 
        properties.put("4", 15); 
        properties.put("Geeks", 20); 
        properties.put("Welcomes", 25); 
        properties.put("You", 30); 
  
        // Print Properties details 
        System.out.println("Current Properties: "
                           + properties.toString()); 
  
        System.out.println("keySet: "
                           + properties.keySet()); 
    } 
}

输出：

Current Properties: {You=30, Welcomes=25, 4=15, Geeks=20}
keySet: [You, Welcomes, 4, Geeks]

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

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注：本文由纯净天空筛选整理自Kirti_Mangal大神的英文原创作品 Properties keySet() method in Java with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。