If, else if, else statement not behaving as expected

**techwiz24** · April 14th, 2011, 06:25 PM

I'm new to java, so if it's stupid simple, forgive me

. I'm trying to parse commandline args using a giant if-else if-else block. Right now, i'm just trying to get it working by displaying the "help" block (tested works fine). Whenever I run the program, it executes the else segment...

public static void main(String[] args) {
		for (String s: args){
			//DebugCode
			System.out.println(s);
			System.out.println(args[0]);
		}
		if (args.length < 1){
			interactive();
		}
		else{
			try{
				//TODO fix
				String dummy;
				String command = String.valueOf(args[0]);
 
				if (command == "-h" || command == "--help"){
					help();
				}else if (command == "-p" || command == "--push"){
					//push	
					dummy = "dummy";
				}else{
					//Invaled option
					System.out.println("Unknown operating mode. Please restart the program");
				}
			}
			catch(Exception ex){
				System.out.println("Error:   " + ex.getStackTrace() + ex.getMessage());
			}
			finally{
 
			}
		}
 
	}

running the program with the -h CLI arg in eclipse prints -h in the first two debuglines, but as soon as it gets to the if-else block, it executes the else...any suggestions? I've also tried args[0] inplace of command

**techwiz24** · April 14th, 2011, 06:26 PM

i've also tried elimating the

... || command == "--help"

segment, but the problem persists

**newbie** · April 14th, 2011, 06:31 PM

Read the following and all will become clear.
http://www.javaprogrammingforums.com...html#post18725
Come back if you're still stuck

**JavaPF** · April 15th, 2011, 04:53 AM

Originally Posted by newbie

Read the following and all will become clear.
http://www.javaprogrammingforums.com...html#post18725
Come back if you're still stuck

newbie is correct, you have made a simple error here. Please read the link provided.

I have also moved this thread to Loops & Control Statements

**techwiz24** · April 15th, 2011, 06:51 AM

Ah. Thank you! It's weird that the == operator doesn't work, but the .equals() method does. I come from basic VB.net and python

, I guess I was trying to do it how I would do it there lol. Thanks for the tip!

On a side note, is there a reason why this doesn't work?

**helloworld922** · April 15th, 2011, 12:02 PM

From the article:

Originally Posted by Common Java Mistakes

The equals operator is used exclusively to compare the value of primitives, or to compare the references (memory addresses) of objects.

The equals() method is used to define when two object values are equal. They do not necessarily have to be the same object (though, if they are they should return true for equals() as well as ==).

To add a little more to this, most objects in Java are referenced by their memory address. When you use the == operator, you're comparing the addresses of two objects. So if you have two distinct object which happen to have the same value, would still have different memory addresses, and == would return false. If you want to test if two objects just happen to have the same value, you use the .equals() method.

Note that for primitives (int, boolean, byte, float, etc.) there's no need for a .equals() method because these don't contain a reference to the value, but rather contain the value itself. However, if you're using wrapper classes (Integer, Float, Boolean, etc.), you must use the .equals() method because now you're holding references to the wrapper object, not the direct value.

.equals() is used because Java doesn't have operator overloading. Python does, so you could overload == to do what the .equals() method does in Java. To allow Python users to still compare memory addresses, Python has the is keyword, which is analogous to Java's == operator.

I've never used VB, so I couldn't say what the equivalent VB code would be

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