Java tutorial for beginners: your first program, explained.

Start with a program that prints one line

Java source code describes instructions using a defined syntax. The example below uses a class named Main and a method named main. A method is a named block of instructions. In this program, main is where execution begins.

Save this complete example as Main.java in a Java development environment, or use a Java editor that provides a Run control. Keep the capital M in the filename and class name. Read the expected output before running it.

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

Understand the main method and braces

The outer pair of braces encloses the class. The inner pair encloses the main method. The print statement belongs inside that method. Indentation makes these relationships easier to see; braces define the blocks.

In this familiar form of a Java entry point, public makes the method accessible, static lets it run without first creating a Main object, and void means the method does not return a value. String[] args is a parameter that can receive command-line arguments. This example does not use those arguments.

You do not need to write your own objects or handle arguments to change the message. Keep the surrounding structure while you practise the statements inside main. As you learn methods and classes, you can return to the role of each part.

Add variables and calculate a total

A variable is a name for a value used by the program. Declare its type and name before using it. String is used here for text; int is used for whole numbers. The equals sign gives each variable its initial value.

public class Main {
    public static void main(String[] args) {
        String student = "Mira";
        int minutesPerDay = 15;
        int days = 4;
        int totalMinutes = minutesPerDay * days;

        System.out.println("Student: " + student);
        System.out.println("Practice minutes: " + totalMinutes);
    }
}

Predict a change before you run it

Keep the same program and change minutesPerDay to 12 and days to 5. Work out the expected total yourself. Then run the program and compare the actual output with your prediction.

Find common mistakes one at a time

Java is case-sensitive: String and string are different names, as are minutesPerDay and MinutesPerDay. Check spelling and capitals before changing the algorithm. Use double quotes for the text in these examples, and keep each statement’s semicolon.

When a compiler reports an error, start with the first message and inspect that line and the line above it. A missing closing quote, brace or semicolon can make later lines appear incorrect too. Correct one cause, run again and inspect the next result.

After these examples, practise conditions, loops and methods. In InterviewSkills coding practice, choose Java and follow the selected problem’s input and output requirements. The labels used in this tutorial explain the output; a coding problem may require only a number, so match its instructions exactly.