Java 7 – try-with-resources Statement

I. Concepts

What is a resource? An object that implements java.lang.AutoCloseable or java.io.Closeable is called a resource.
Some Java resource classes:
– java.io.BufferedReader.BufferedReader
– java.net.Socket.Socket
– java.sql.Statement
…
try-with-resources statement ensures that each resource is closed after completed execution of the statement.

II. Practice

For see benifits of try-with-resources statement, JavaSampleApproach makes an sample with BufferedReader for reading a text file.

1. Use Java6 or early version and Problems

package com.javasampleapproach.trywithresources;

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

public class ReadFileByJava6OrEarly {
	public static void main(String[] args) {
        BufferedReader br = null;
        try {
            br = new BufferedReader(new FileReader("C://readfile/input.txt"));
            String line;
            while (null != (line = br.readLine())) {
                // process each line of File
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (null != br)
                    br.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

– After reading a file, we take a risk if developers do Not remember to close resources.

– Source code is not clear & clean:

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

So how to improve it?

2. Java 7 – New Approach by try-with-resources statement

By try-with-resources statement, our code is clear and clean. Developers do NOT need to close the resources so one risk is auto removed.

package com.javasampleapproach.trywithresources;

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

public class ReadFileWithJava7 {
	public static void main(String[] args) {
        try (BufferedReader br = new BufferedReader(new FileReader("C://readfile/input.txt"))) {
            String line;
            while (null != (line = br.readLine())) {
                // processing each line of file
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

That is better? Right!

IV. Source code

Java7TryWithResource