try with Resources

In Java try with resources, a resource is an object it may be File resource or Database connection resource or Network connection resource and that resource must be closed after completed the program.

Before Java 1.7 version

In Java 1.6 or early version, try block is used to open the resource and after completed the usage of the resource we must close that resource explicitly in a finally block.

package com.exceptions;

public class Test {

       try{

              //Open resources like File resource, Database connection resource etc.

       }

       catch (IOException e) {

              // Handling Exceptions

       }finally{

              // Close resources

       }

}

Example for close resource in finally block

In this program,  we created a resource BufferedReader object and pointing it myfile.txt. If any choice occurs exception that should handle by the catch block and after completed the usage of resource we closed resource explicitly in finally block.

The main drawbacks are here:

=> The length of the program code increase and readability of program decrease

=> Programmer must close the resources explicitly

=> More complexity to the programmer.

package com.exceptions;

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

public class Test {

       public static void main(String[] args) {

              BufferedReader br = null;

              try {

                     br = new BufferedReader(new FileReader("D:\\myfile.txt"));

                     System.out.println(br.readLine());

              }

              catch (IOException e) {

                     System.out.println(e);

              }

              finally {

                    

                           if (br != null)

                                  try {

                                         br.close();

                                  } catch (IOException e) {

                                         System.out.println(e);

                                  }                   

              }

       }

}

From Java 1.7 version

From Java 1.7 version onwards we don’t need to close the resource explicitly in the finally block, resources are closed automatically after executed the try and catch blocks.

     try(/* Open resources here */){

           // Use resources

       } catch (IOException e) {

              // Handling Exception

       }

      

In this program, we don’t need to close resource explicitly in finally block, what are the resources are opened in try those resources closed automatically after executed the try and catch blocks.

The main use of try with resources:

=> The length of the program code decrease and readability of the program increase

=> Developer no need to close the resources explicitly

=> No need of finally block and easy to write for developer

try with resource example

package com.exceptions;

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

public class Test {

       public static void main(String[] args) {       

              try(BufferedReader br

                           = new BufferedReader(new FileReader("D:\\myfile.txt"))) {                 

                     String line=br.readLine();

                     while(line!=null){

                           System.out.println(line);

                           line=br.readLine();

                     }

              }

              catch (IOException e) {

                     System.out.println(e);

              }            

       }

}

Try with multiple resources

We can open multiple resources in the try-resources statement separated by a semicolon(;).

try(/*Resource1; Resource2; Resource3*/){      

       //use resources

}

catch(IOException e){

       //handle exceptions

}

Example for a try with multiple resources:

package com.exceptions;

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

import java.io.PrintWriter;

public class TryWithResources {

       public static void main(String[] args) {       

              try(BufferedReader br

                           = new BufferedReader(new FileReader("D:\\myfile.txt"));

                           PrintWriter pw=new PrintWriter("D:\\newfile.txt")   ) {

                     //we can read a file and write a file

              }

              catch (IOException e) {

                     System.out.println(e);

              }            

       }

}