Java 中的属性键集()方法，示例

原文:https://www . geesforgeks . org/properties-key set-method-in-Java-with-examples/

属性类 的键集()方法用于创建属性中包含的一组关键元素。它基本上返回一个键的集合视图，或者我们可以创建一个新的集合并将键元素存储在其中。

语法:

public Set keySet()

参数:该方法不接受参数

返回:该方法返回包含在该属性对象中的键的集合视图。

下面的程序展示了 int keySet()方法的实现。

程序 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]

程序二:

// 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]

参考资料:https://docs . Oracle . com/javase/9/docs/API/Java/util/properties . html # KeySet–

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