Revision as of 15:36, 20 November 2007

COMP 1010 Home > Java Fundamentals

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Printing Text to the Screen

To print text to the screen you can use:

System.out.println("text");

or

System.out.print("text");

Whatever you put inside of the quotes in place of text will be printed to the screen. The difference between the two is System.out.println() will print a newline after the text unlike System.out.print() which just prints the text as-is. The examples that follow demonstrate the usage of these two output methods.

Example 1

This program prints the message "Go Bisons!" to the screen.

public class Output1
{
  public static void main(String args[]) 
  {
    System.out.println("Go Bisons!");
  }
}

Example 2

This program prints the message "Go Bisons!" to the screen three times, on separate lines.

public class Output2
{
  public static void main(String args[]) 
  {
    System.out.println("Go Bisons!");
    System.out.println("Go Bisons!");
    System.out.println("Go Bisons!");
  }
}

Output

Go Bisons!
Go Bisons!
Go Bisons!

Example 3

Now, lets compare this program to the one in example 2. This program also prints the message "Go Bisons!" to the screen three times. However, it does not print a new line after each message.

public class Output3
{
  public static void main(String args[]) 
  {
    System.out.print("Go Bisons!");
    System.out.print("Go Bisons!");
    System.out.print("Go Bisons!");
  }
}

Output

Go Bisons!Go Bisons!Go Bisons!

Printing Variables with System.out.println()

You can also print the contents of a variable by using System.out.println(). The following examples demonstrate how to do this.

Example 1

public class PrintVariable
{
  public static void main(String args[]) 
  {
    int num;

    num = 5;

    System.out.println(num);
  }
}

Output

5

In this example we create an integer called num and use it to store the number 5. We then print the contents of num by using System.out.println(). Notice that we did not put quotes around num. Variables do not need to be put in quotes. Only a string of text needs to be put inside of quotes.

Example 2

In this example we will show you how to print a string of text followed by a variable.

public class PrintTemp
{
  public static void main(String args[]) 
  {
    int temp;

    temp = 25;

    System.out.println("The temperature is currently " + temp);
  }
}

Output

The temperature is currently 25

Note that since only text in the quotes is printed, we need to include a space after currently to produce one in the output.

Example 3

We can also put the variable in the middle of a sentence.

public class PrintTemp
{
  public static void main(String args[]) 
  {
    int temp;

    temp = 25;

    System.out.println("The temperature is currently " + temp + " degrees Celsius.");
  }
}

Output

The temperature is currently 25 degrees Celsius.

We use a + sign to join a string of text and a variable. More information on creating Strings expressions can be found in the string section.