Java Syntax
In the previous chapter, we created a Java file called MyClass.java, and we used the following code to print "Hello World" to the screen:
MyClass.java
public class MyClass {
public static void main(String[] args) {
System.out.println("Hello World");
}
}
Example explained
Every line of code that runs in Java must be inside a class
.
In our example, we named the class MyClass. A class should always start with
an uppercase first letter.
Note: Java is case-sensitive: "MyClass" and "myclass" has different meaning.
The name of the java file must match the class name. When saving the file, save it using the class name and add ".java" to the end of the filename. To run the example above on your computer, make sure that
Java is properly installed: Go to the Get Started Chapter for how to install Java. The output should be:
Hello World
The main Method
The main()
method is required and you will
see it in every Java
program:
public static void main(String[] args)
Any code inside the main()
method will be executed. You don't have to understand the keywords before and after main. You will get to know
them bit by bit while reading this tutorial.
For now, just remember that every Java program has a class
name which
must match the filename, and that every program must contain the
main()
method.
System.out.println()
Inside the main()
method, we can use the println()
method to print a line of text to the screen:
public static void main(String[] args) {
System.out.println("Hello World");
}
Note: The curly braces {}
marks the beginning and the end of a block of code.
Note: Each code statement must end with a semicolon.
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