Printing - AP Computer Science A

Printing variables to the console

We previously looked at a line of code like this:

Java

System.out.println("Hello World");

It prints the line of Hello World to the screen. If we change the string inside to Greg Heffley, it will print out Greg Heffley.

From now on, we will be writing all our code inside the main method. If we don't, the lesson will clearly say where you should be writing your code.

Let's this a few steps further. Let's create some variables and see how they are printed.

Java

String name = "Rowley Jefferson";
int age = 14;
double pi = 3.14159265;
char ch = 'Z';
boolean isAdult = false;

System.out.println(name);
System.out.println(age);
System.out.println(pi);
System.out.println(ch);
System.out.println(isAdult);

The output for the console looks like this:

Text

Rowley Jefferson
14
3.14159265
Z
false

There are a few things to notice here:

We can print all primitive types
We can use variables instead of directly writing the value
When multiple printlns are used, they stack

This is important to know, or else your code would be very messy and inefficient.

print

We have used System.out.println so far, but did you know there is a System.out.print as well? Let's see what happens if we use our previous example without println and with print instead.

Java

System.out.print(name);
System.out.print(age);
System.out.print(pi);
System.out.print(ch);
System.out.print(isAdult);

Here's the output:

Text

Rowley Jefferson143.14159265Zfalse

And there's the main difference: There aren't any line breaks! print differs from println in that it doesn't print content on new lines, but the same line.

Try playing around with a mixture of both print and println.

Java

System.out.println(name);
System.out.print(age);
System.out.println(pi);
System.out.print(ch);
System.out.print(isAdult);