try with resources

Today I learned about the try-with-resources Statement that was included with Java 7. To quote the docs:

• “A resource is an object that must be closed after the program is finished with it.”
• “The try-with-resources statement ensures that each resource is closed at the end of the statement”
• “Any object that implements java.lang.AutoCloseable…can be used as a resource”

The basic gist here is that, when using a class that implements AutoCloseable / Closeable, we no longer have to include a finally block that closes the resource.

Here’s an example using the Apache CuratorFramework:

package com.lombardo.demo;

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;

public class CuratorService {
    private String zkConnectString = "localhost:2181";
    private ExponentialBackoffRetry retryPolicy = new ExponentialBackoffRetry(1000, 3);

    public String createNode(String path, String data) throws Exception {
        // passing in a 'Closable' CuratorFramework instance to the try statement
        try(CuratorFramework client = CuratorFrameworkFactory.newClient(zkConnectString, retryPolicy)) {
            client.start();
            return client.create().creatingParentContainersIfNeeded().forPath(path);
        }
        // .close() was called automatically
    }
}

as opposed to the finally block method:

public String createNodeOldSchool(String path, String data) throws Exception {
    CuratorFramework client = CuratorFrameworkFactory.newClient(zkConnectString, retryPolicy);
    try {
        client.start();
        return client.create().creatingParentContainersIfNeeded().forPath(path);
    } finally {
        client.close();
    }
}