• Java
    • JAXB Tutorial
      • What is JAXB
      • JAXB Marshalling Example
      • JAXB UnMarshalling Example
  • Spring Tutorial
    • Spring Core Tutorial
    • Spring MVC Tutorial
      • Quick Start
        • Flow Diagram
        • Hello World Example
        • Form Handling Example
      • Handler Mapping
        • BeanNameUrlHandlerMapping
        • ControllerClassNameHandlerMapping
        • SimpleUrlHandlerMapping
      • Validation & Exception Handling
        • Validation+Annotations
        • Validation+ResourceBundle
        • @ExceptionHandler
        • @ControllerAdvice
        • Custom Exception Handling
      • Form Tag Library
        • Textbox Example
        • TextArea Example
        • Password Example
        • Dropdown Box Example
        • Checkboxes Example
        • Radiobuttons Example
        • HiddenValue Example
      • Misc
        • Change Config file name
    • Spring Boot Tutorial
  • Hibernate Tutorial
  • REST Tutorial
    • JAX-RS REST @PathParam Example
    • JAX-RS REST @QueryParam Example
    • JAX-RS REST @DefaultValue Example
    • JAX-RS REST @Context Example
    • JAX-RS REST @MatrixParam Example
    • JAX-RS REST @FormParam Example
    • JAX-RS REST @Produces Example
    • JAX-RS REST @Consumes Example
    • JAX-RS REST @Produces both XML and JSON Example
    • JAX-RS REST @Consumes both XML and JSON Example
  • Miscellaneous
    • JSON Parser
      • Read a JSON file
      • Write JSON object to File
      • Read / Write JSON using GSON
      • Java Object to JSON using JAXB
    • CSV Parser
      • Read / Write CSV file
      • Read/Parse/Write CSV File – OpenCSV
      • Export data into a CSV File
      • CsvToBean and BeanToCsv – OpenCSV

JavaInterviewPoint

Java Development Tutorials

Java Try-with-Resources | Java 9 Try with Resources Improvements

October 15, 2018 by javainterviewpoint Leave a Comment

Java Try-with-Resources was first introduced in Java 7 to manage the resource automatically. The try-with-resources statement received a major change in Java 9 which simplifies the code. In this post, we will discuss the what is try-with-resource statement and the improvements made to it in Java 9.

What is Java Try with Resources statement?

Before getting to the improvements made to the Try with Resources statement, let’s understand what is try with resources statement ?

The try-with-resources statement can define one or more resources which must be closed at the end of the program execution. The try-with-resources block ensures that each resource is closed at the end of the execution. Any object that implements java.lang.AutoCloseable can be passed as a resource.

Before Java 7

Before Java 7, while reading a file we need to close the Readers manually inside the finally block.

In the below code we are reading a file in Java, we have two resources FileReader and BufferedReader which is closed in the finally block. Which is a boilerplate which we needs to be handled by the developer.

package com.javainterviewpoint;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class JavaReader
{
	public static void main(String[] args) throws IOException
	{
		FileReader fileReader = null;
		BufferedReader bufferedReader = null;

		try
		{
			fileReader = new FileReader("E:\\jip\\test.txt");
			bufferedReader = new BufferedReader(fileReader);

			String line;

			while ((line = bufferedReader.readLine()) != null)
			{
				System.out.println(line);
			}

		} catch (IOException e)
		{
			e.printStackTrace();
		} finally
		{
			try
			{
				if (bufferedReader != null)
					bufferedReader.close();
				if (fileReader != null)
					fileReader.close();
			} catch (IOException ex)
			{
				ex.printStackTrace();
			}
		}
	}
}

After Java 7

After the introduction of try-with-resources statement in Java 7 there is no necessity to use of finally block. The required resources will be opened inside the try brackets and will be auto closed regardless of whether the program completes normally or terminates abruptly.

package com.javainterviewpoint;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class JavaReader
{
	public static void main(String[] args) throws IOException
	{
		try (BufferedReader bufferedReader = new BufferedReader(new FileReader("E:\\jip\\test.txt")))
		{

			String line;

			while ((line = bufferedReader.readLine()) != null)
			{
				System.out.println(line);
			}

		} catch (IOException e)
		{
			e.printStackTrace();
		}
	}
}

In the above we can see that we have created the instance of the FileReader and BufferedReader inside the try and we have not used the finally block to close the opened resources as it will be closed automatically by the try-with-resources statement.

Java 9 try-with-resources Statement

Java Try with Resources

Issue with Java 7 try-with-resources – Resource declared outside

However there is a small issue which occurs with the try-with-resources statement of Java 7, it will not allow the resources which is created outside the try block. It throws the compilation error.

Let’s take a look into the below code.

We have created the BufferedReader outside the try block and have passed the reference alone to the try.

package com.javainterviewpoint;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class JavaReader
{
    public static void main(String[] args) throws IOException
    {
        BufferedReader bufferedReader = new BufferedReader(new FileReader("E:\\jip\\test.txt"));
        try (bufferedReader)
        {

            String line;

            while ((line = bufferedReader.readLine()) != null)
            {
                System.out.println(line);
            }

        } catch (IOException e)
        {
            e.printStackTrace();
        }
    }
}

Output:

Exception in thread "main" java.lang.Error: Unresolved 
compilation problems: 
  Syntax error, insert "VariableDeclaratorId = VariableInitializer" 
to complete Resources
  bufferedReader cannot be resolved to a type

  at com.javainterviewpoint.JavaReader.main(JavaReader.java:13)

Workaround in Java 7

In order to overcome above issue in Java 7, we have to do a workaround. We have to create a local reference in the try and the code will execute properly.

In the below code we have refereed the bufferedReader with the local variable newBufferedReader within the try

package com.javainterviewpoint;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class JavaReader
{
    public static void main(String[] args) throws IOException
    {
        BufferedReader bufferedReader = new BufferedReader(new FileReader("E:\\jip\\test.txt"));
        try (BufferedReader newBufferedReader = bufferedReader)
        {
            String line;

            while ((line = newBufferedReader.readLine()) != null)
            {
                System.out.println(line);
            }

        } catch (IOException e)
        {
            e.printStackTrace();
        }
    }
}

This issues has been addressed in Java 9, now try-with-resources Statement allows you to declare the resource outside and no need to create a local reference to access the resource. The code which failed in Java 7 would run perfectly in Java 9.

package com.javainterviewpoint;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class JavaReader
{
    public static void main(String[] args) throws IOException
    {
        BufferedReader bufferedReader = new BufferedReader(new FileReader("E:\\jip\\test.txt"));
        try (bufferedReader)
        {

            String line;

            while ((line = bufferedReader.readLine()) != null)
            {
                System.out.println(line);
            }

        } catch (IOException e)
        {
            e.printStackTrace();
        }
    }
}

Output:

Welcome to JavaInterviewPoint!!!

Other interesting articles which you may like …

  • Constructor in Java
  • Private Constructors in Java
  • Java Constructor Chaining with example
  • Java – Constructor in an Interface?
  • Constructor.newInstance() method
  • Parameterized Constructor in Java
  • Java 8 – Lambda Expressions
  • Java 8 – ForEach Example
  • Java 8 Default Methods in Interface
  • Multiple Inheritance in Java 8 through Interface
  • Java 9 – jdeprscan
  • Private Methods in Interfaces Java 9
  • Java Method Overloading Example
  • Java Constructor Overloading Example
  • Java this keyword | Core Java Tutorial
  • Java super keyword
  • Abstract Class in Java
  • Interface in Java and Uses of Interface in Java
  • What is Marker Interface
  • Serialization and Deserialization in Java with Example
  • Generate SerialVersionUID in Java
  • Java Autoboxing and Unboxing Examples
  • Use of Java Transient Keyword – Serailization Example
  • Use of static Keyword in Java
  • What is Method Overriding in Java
  • Encapsulation in Java with Example
  • Final Keyword in Java | Java Tutorial
  • Java Static Import
  • Java – How System.out.println() really work?
  • Java Ternary operator
  • Java newInstance() method

Filed Under: Core Java, Java Tagged With: java 9, Java 9 Try with Resources, Java Try-with-Resources, Try-with-Resources

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Java Basics

  • JVM Architecture
  • Object in Java
  • Class in Java
  • How to Set Classpath for Java in Windows
  • Components of JDK
  • Decompiling a class file
  • Use of Class.forName in java
  • Use Class.forName in SQL JDBC

Oops Concepts

  • Inheritance in Java
  • Types of Inheritance in Java
  • Single Inheritance in Java
  • Multiple Inheritance in Java
  • Multilevel Inheritance in Java
  • Hierarchical Inheritance in Java
  • Hybrid Inheritance in Java
  • Polymorphism in Java – Method Overloading and Overriding
  • Types of Polymorphism in java
  • Method Overriding in Java
  • Can we Overload static methods in Java
  • Can we Override static methods in Java
  • Java Constructor Overloading
  • Java Method Overloading Example
  • Encapsulation in Java with Example
  • Constructor in Java
  • Constructor in an Interface?
  • Parameterized Constructor in Java
  • Constructor Chaining with example
  • What is the use of a Private Constructors in Java
  • Interface in Java
  • What is Marker Interface
  • Abstract Class in Java

Java Keywords

  • Java this keyword
  • Java super keyword
  • Final Keyword in Java
  • static Keyword in Java
  • Static Import
  • Transient Keyword

Miscellaneous

  • newInstance() method
  • How does Hashmap works internally in Java
  • Java Ternary operator
  • How System.out.println() really work?
  • Autoboxing and Unboxing Examples
  • Serialization and Deserialization in Java with Example
  • Generate SerialVersionUID in Java
  • How to make a class Immutable in Java
  • Differences betwen HashMap and Hashtable
  • Difference between Enumeration and Iterator ?
  • Difference between fail-fast and fail-safe Iterator
  • Difference Between Interface and Abstract Class in Java
  • Difference between equals() and ==
  • Sort Objects in a ArrayList using Java Comparable Interface
  • Sort Objects in a ArrayList using Java Comparator

Follow

  • Coding Utils

Useful Links

  • Spring 4.1.x Documentation
  • Spring 3.2.x Documentation
  • Spring 2.5.x Documentation
  • Java 6 API
  • Java 7 API
  • Java 8 API
  • Java EE 5 Tutorial
  • Java EE 6 Tutorial
  • Java EE 7 Tutorial
  • Maven Repository
  • Hibernate ORM

About JavaInterviewPoint

javainterviewpoint.com is a tech blog dedicated to all Java/J2EE developers and Web Developers. We publish useful tutorials on Java, J2EE and all latest frameworks.

All examples and tutorials posted here are very well tested in our development environment.

Connect with us on Facebook | Privacy Policy | Sitemap

Copyright ©2023 · Java Interview Point - All Rights Are Reserved ·