Java 9 Try with Resource Enhancement

Java introduced try-with-resources feature in Java 7 that helps to close resources automatically after being used.

In other words, we can say that we don’t need to close resources (file, connection etc) explicitly, try-with-resource close that automatically by using the AutoClosable interface.

If you look in Java 7 then you will find that try-with-resources has a limitation that It requires resources to declare locally within its block Like below.

Example Java 7 Resource Declared within resource block

try(FileOutputStream fileStream=new FileOutputStream(“test.txt”);){

}

This code will be executed fine in Java 7 and even with Java 9 because Java maintains its legacy or backward compatibility.

But the below program would not work with Java 7 because we can’t put resource declared outside the try-with-resource.

If we execute this code in Java 7, the compiler generates an error message.

FileOutputStream fileStream=new FileOutputStream(“test.txt”);

try(fileStream){

}

To overcome this error, try-with-resource is enhanced in Java 9 and now we can use reference of the resource that is not declared locally.

test.txt

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Java9TryWithResourcTest.java

package com.kkjavatutorials.org;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Scanner;

/*
 * Java 9 Try With Resource Enhancement Feature
 */
public class Java9TryWithResourcTest {

	public static void main(String[] args) throws IOException  {
		InputStream inputStream = new FileInputStream("test.txt");
		Scanner scanner = new Scanner(inputStream);
		try(inputStream;scanner) {
			
			while(scanner.hasNextLine()) {
				System.out.println(scanner.nextLine());
			}
		} catch (Exception e) {
			e.printStackTrace();
	}
	}
}

package com.kkjavatutorials.org;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.util.Scanner;

* Java 9 Try With Resource Enhancement Feature

public class Java9TryWithResourcTest {

public static void main(String[] args) throws IOException {

InputStream inputStream = new FileInputStream("test.txt");

Scanner scanner = new Scanner(inputStream);

try(inputStream;scanner) {

while(scanner.hasNextLine()) {

System.out.println(scanner.nextLine());

}

} catch (Exception e) {

e.printStackTrace();

}

If you run Java9TryWithResourcTest.java as Java Application then it will give the below output:

Let's learn java 9 feature.
Learning java is fun..

1 2	Let's learn java 9 feature. Learning java is fun..

That’s all about Java 9 Try with Resource Enhancement

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Java 9 Collection Factory Methods
Java 9 Stream API improvements

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