Java中的属性列表（PrintWriter）方法与示例

Properties 类的list(PrintWriter)方法用于将此 Properties 列表打印到指定的输出流，作为参数传递。此方法可用于调试目的，因为它可以帮助查看流上的 Properties 元素。0

句法：

public void list(PrintWriter out)

参数：此方法接受参数PrintWriter out ，它是要在其上打印 Properties 元素的输出流。

返回：此方法仅打印元素，不返回任何内容。

异常：如果此属性列表中的任何键不是字符串，此方法将引发ClassCastException 。

下面的程序显示了 int list(PrintWriter) 方法的实现。

方案一：

// Java code to show the implementation of
// list(PrintWriter) method
  
import java.util.*;
import java.io.*;
  
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());
  
        PrintWriter writer = new PrintWriter(System.out);
  
        // print the list with a PrintWriter object
        properties.list(writer);
  
        // flush the stream and display
        System.out.println("listing out the Properties: ");
        writer.flush();
    }
}

输出：

Properties: {Book=500, Mobile=5000, Pen=10, Clothes=400}
listing out the Properties: 
-- listing properties --
Book=500
Pen=10
Mobile=5000
Clothes=400

方案二：

// Java program to demonstrate
// list(PrintWriter) method.
  
import java.util.*;
import java.io.*;
  
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("Properties: "
                           + properties.toString());
  
        PrintWriter writer = new PrintWriter(System.out);
  
        // print the list with a PrintWriter object
        properties.list(writer);
  
        // flush the stream and display
        System.out.println("listing out the Properties: ");
        writer.flush();
    }
}

输出：

Properties: {You=30, Welcomes=25, 4=15, Geeks=20}
listing out the Properties: 
-- listing properties --
You=30
4=15
Welcomes=25
Geeks=20

参考资料：https://docs.oracle.com/javase/9/docs/api/ Java/util/Properties.html#list-java.io.PrintWriter-