Compile and Run Java Programs in One Click!

Here is how we can compile and run Java programs in one click. Yes, you heard it right and that is absolutely true. What about commands? Do i need to write them. Of course, you need them, but you don't need them to type always.

Creating a batch file lets you do this. In this post you'll learn how to compile all Java programs, wait till the output is seen, hide the echo as well!

Before we start, let us talk a bit about the batch files.

1. They are the files which contains a set of commands that are executed in the command prompt one by one.
2. They are saved with a .bat extension.
3. Whenever you click on that file, those commands are executed one after the other.

So, it is clear that you need to write the two commands that compile and execute your program. They are javac MyProgram.java and
java MyProgram
OK. That's it? Can we just include these two lines and save the batch file? Hmm, but you can't see the output, unless it is a GUI program. Because, the output is printed and the command prompt is closed. That's it. Now, is there a solution? Yes, here it is.

Pause batch file to display output

@echo off
javac MyProgram.java
java MyProgram
pause

The pause command stops the command prompt from exiting.
The @echo off command doesn't display the path of the directory in the command prompt. For instance, if you are executing this in the folder E:\java then E:\java> is not visible. Just see it in practice for a clear understand.

Though there are any errors, then the second command is executed. The program will run depending upon the previous class file (if any). Otherwise, could not find or load main class MyProgram error will be displayed.
To prevent this, you can delete the previous class file and that command should be placed before.

Stop executing previous class file code [Use with caution]

@echo off

del MyProgram.class

javac MyProgram.java

java MyProgram

pause

I recommend you to use this with caution, once the previous class file is deleted, you might not get back your code. Your program stays fine, but it is a modified version that contains errors.

One last tip, to compile all the classes, use javac *.java

@echo off

javac *.java

pause

However, you cannot execute all programs at a time. You'll need to write one by one.

Writing and saving them?

Simple,

1. Write those commands in notepad and save them in the directory where your Java programs are present.
2. Click on that batch file, every time you write it!
3. To make your life more easy, just create a shortcut for that batch file on your desktop

and here we go, click it every time to compile and run!

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Image credit: logopond.com

Why should we write setVisible() at last?

In many posts, I have been mentioning to push down the setVisible() to last, Did I? But why? I think, I have not mentioned a reason before. Now, I decided to write this post with enthusiasm. The reason is I'm going to make it a bit funny with an analogy.

You know that setVisible() is used to make a component visible. Mostly we will be using it to show JFrame. Fine, until recently I have been writing setVisible() at the top before adding all the components. Then, I recently started turning the game around.

Why push add() to the top? (The analogy, the fun!)

You can make a JFrame visible before adding the components. Right? But how will it look? Consider a general life situation, say you want to go out for a party.. You get ready before you attend the party, you bath, dress up, makeup. But how will it look when you do after attending/in the party? Just imagine!! Lol!

You'll need to do the complete make up before you make the frame ready to get displayed. Fine.

Also, writing setLocationRelativeTo() before sizing the frame will not give the desired effect because it depends upon the size of the frame. So the frame needs to have a size before it's location is set relative to something. If its size is changed after the location is set, then you got an undesired output. So, be careful. See the following program, you get an undesired output if you execute it.

import javax.swing.*;
class LocationFail
{
    public static void main(String args[])
    {
        JFrame f=new JFrame("My Frame");
        f.setVisible(true);
        
        f.setLocationRelativeTo(null);
        
        // the wrong thing!!
        // doesn't appear at the center
        f.setSize(400,400);
    }
}

Even when you are working with pack() you need to add all the components first, pack the frame and then invoke setLocationRelativeTo() and then setVisible(), now this looks great!

Are there any analogies or counter arguments that you would love to fire on me? Discuss them in comments below.

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“If you can imagine it, you can achieve it; if you can dream it, you can become it.” - William Arthur Ward