Java Output

Printing to the console

The most common way to show output in Java is System.out.println, which prints a value and then moves to a new line. It is the tool you will reach for constantly while learning, both to display results and to check what your program is doing.

public class Main {
  public static void main(String[] args) {
    System.out.println("Hello, World!");
    System.out.println("Each println starts a new line.");
  }
}

println versus print

System.out.print works just like println but does not add a new line at the end, so the next output continues on the same line. Use print when you want to build a line piece by piece and println when you want each value on its own line.

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

Printing numbers and expressions

You can print numbers directly, without quotation marks. If you place a math expression inside the print, Java calculates the result first and then prints it. Text must be wrapped in double quotes, but numbers must not be, or they will be treated as text instead of values.

public class Main {
  public static void main(String[] args) {
    System.out.println(42);
    System.out.println(10 + 5);
    System.out.println("Total: " + (10 + 5));
  }
}

Common pitfalls

• Text values must be inside double quotes: "like this"
• Numbers used as values must not be quoted, or they become text
• System, out, and println are case-sensitive and must be spelled exactly
• Each print statement still needs a semicolon at the end