In this section, you will learn how to read the key-value of properties files in Java.

Read the Key-Value of Properties Files in Java

     

In this section, you will learn how to read the key-value of properties files in Java. This section provides you an example for illustration how to read key and it's regarding values from the properties file.

Program Result:

This program takes a property file name and reads values according to the keys if  the mentioned file exists, otherwise it shows the appropriate messages like: " File not found!" and gives you a chance for entering properties file name through the message "Enter file name that has properties extension:". This message is shown until the entered file name exists. If the file name exists then  it takes the key and shows the values behalf the entered key. 

Code Description:

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

Properties():
This is the constructor of Properties class. Properties class extends the Hashtable. This is the class of java.util.* package. Above constructor creates an empty property list, which hasn't any default values. It uses the Keys and key-values of the properties file.

pro.load(InputStream in):
Above method reads the list of keys and values (properties) from the given input stream. InputStream name is passed through the method as a parameter.

pro.getProperty(String key_name):
This method finds the values of the given key in the list of the keys and values from the stream. Key name is passed through the method as a parameter.

Here is the code of program:

import java.io.*;
import java.util.*;

public class ReadProperty{
  String str, key;
  public static void main(String[] args) {
    ReadProperty r = new ReadProperty();
  }
  public ReadProperty(){
    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();
        File f = new File(str + ".properties");
        if(f.exists()){
          Properties pro = new Properties();
          FileInputStream in = new FileInputStream(f);
          pro.load(in);
          System.out.print("Enter Key : ");
          key = bf.readLine();
          String p = pro.getProperty(key);
          System.out.println("Value : " + p);
        }
        else{
          check = 0;
          System.out.println("File not found!");
        }
      }
    }
    catch(IOException e){
    System.out.println(e.getMessage());
    }
  }
}

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