Java - Interning

public static void main(String[] args) {

    Long long1 = new Long(1234);
    Long long2 = long1;

    // Does this compare references or actual values? 

    if (long1 == long2) {
        System.out.println("Equal");
    } else {
        System.out.println("Not Equal");
    }

    // Displays "Equal"

    long2 = new Long(1234);

    // Let's create a new object with the same value to see if this works.

    if (long1 == long2) {
        System.out.println("Equal");
    } else {
        System.out.println("Not Equal");
    }

    // Displays "Not Equal" 

    // Let's compare the Long wrapper with its equivalent primitive. 

    if ((new Long(1234) == 1234) && (Long.valueOf(1234) == 1234)) {
        System.out.println("Equal");
    } else {
        System.out.println("Not Equal");
    }

    // Displays "Equal" 

    long1 = Long.valueOf(1234);
    long2 = Long.valueOf(1234);

    // We've now used valueOf() instead of creating a new Long, just to see if it works. 

    if (long1 == long2) {
        System.out.println("Equal");
    } else {
        System.out.println("Not Equal");
    }

    // Displays "Not Equal"   

    // Numbers in the range [-128, 127] are cached. 

    long1 = (Long.valueOf(127);

    long2 = (Long.valueOf(127);

    if (long1 == long2) {
        System.out.println("Equal");
    } else {
        System.out.println("Not Equal");
    }

    // Displays "Equal" 

    // So let's prove it for numbers greater than 127. 

    if ((Long.valueOf(128) == Long.valueOf(128))) {
        System.out.println("Equal");
    } else {
        System.out.println("Not Equal");
    }

    // Displays "Not Equal" 

 }

Java - Difference between System.gc() and Runtime.getRuntime().gc()

public static void main(String[] args) {
    // Some code here

    // Invoke the Garbage Collector here.

     System.gc();

    // Some more code here

    // Invoke the Garbage Collector again.

     Runtime.getRuntime().gc();
}

In the above code, both calls seem to invoke the Garbage Collector. So what is the difference between System.gc() and Runtime.getRuntime().gc()?

Looking at the API documentation for System.gc() it invokes Runtime.getRuntime().gc()which means they are the same and System.gc() is only a convenience method.

Java 8 - Syntax to represent Lambdas

Below is the syntax for representing a Lambda expression :

parameter(s) −> expression(s)

where

• parameter(s) has the following rules:

1. Optional type declaration
2. Optional comma, only for more than one parameter
3. Optional brackets, only for more than one parameter

• expression(s) has the following rules:

1. Optional curly braces
2. Optional return keyword

As quoted from the Oracle site:

"Note that a lambda expression looks a lot like a method declaration; you can consider lambda expressions as anonymous methods—methods without a name."

Java 8 - List of New Features

Among the loads of features added in Java 8, a summary of the most significant features is provided below:

• Lambda Expressions - enables you to treat functionality as a method argument
• Method References - easy to read lambda expressions for methods
• Default Methods -  new functionality added to interfaces
• Stream API -  functional style operations on collections of elements 
• Performance Improvement for HashMaps with Key Collisions
• Java Tool Updates - New jdeps and jjs commands.
  
• New Date Time API - New package for Date and Time
• java.io and java.util Changes - Updates to these packages
  
• Nashorn Javascript Engine

For a more detailed information on all the updates, follow this link to the Oracle site.

More information provided on my blog as well. Follow the Java 8 link in the Labels section at the bottom of this post for more information. Oh, and feel free to drop some comments, whether you find the posts helpful or not.

Happy coding!