Java Properties keySet()用法及代碼示例

Properties類的keySet()方法用於從Properties中包含的關鍵元素中創建一個集合。它本質上返回鍵的集合視圖，或者我們可以創建一個新集合並將鍵元素存儲在其中。

用法:

public Set keySet()

參數：此方法不接受任何參數

返回值：此方法返回此Properties對象中包含的鍵的Set視圖。

下麵的程序顯示int keySet()方法的實現。

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()); 
    } 
}

輸出：

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()); 
    } 
}

輸出：

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

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

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注：本文由純淨天空篩選整理自Kirti_Mangal大神的英文原創作品 Properties keySet() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。