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Write Keys and Values to the Properties file in Java

                         

In this section, you will learn how to write keys and values in the properties files through the Java program. The program for writing keys and values to the properties file has been mentioned just ahead.

Program Result Description:

This program takes a file name and checks whether the file exists or not. If the file exists then it performs the next operations, otherwise shows the appropriate message like: "File not found!" and then gives you one more chance for entering the file name of the properties file by showing the message "Enter file name which has properties extension :". This message is shown until the entered file exists. If the properties file exists then the key and it's regarding value has to be entered which has to be written to the properties file.

Here, the following methods and APIs are explained as follows which have been used in the program:

pro.setProperty(String key, String val):
This method takes keys and it's degrading values and puts into the properties file list through the help of hash table.

pro.store((OutputStream out), null):
This is the method that can be used to write or store the keys and values in properties file list. The OutputStream used when you use the load() method in the program. It takes the OutputStream and comments, but here the only used to OutputStream and no any header or comments( as like descriptions of the properties list).

Here is the code of program:

import java.io.*;
import java.util.*;

public class WriteProperty{
  String str, key, val;
  public static void main(String[] args) {
    WriteProperty w = new WriteProperty();
  }
  public WriteProperty(){
    try{  
            int check=0;
            while(check == 0){
        check=1;
        BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Enter file name which has properties extension:");
        str = bf.readLine();
        Properties pro = new Properties();
        File f = new File(str + ".properties");
        if(!f.exists()){
          check=0;
          System.out.println("File not found!");
        }
        else{
          FileInputStream in = new FileInputStream(f);
          pro.load(in);
          System.out.print("Enter Key : ");
          key = bf.readLine();
          System.out.print("Enter Value : ");
          val = bf.readLine();
          pro.setProperty(key, val);
          pro.store(new FileOutputStream(str + ".properties"),null);
          System.out.println("Operation completly successfuly!");
        }
      }
    }
    catch(IOException e){
    System.out.println(e.getMessage());
    }
  }
}

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