Display Variables
The println() method is often used to display variables.
To combine both text and a variable, use the + character:
Example
String name = "John";
System.out.println("Hello " + name);You can also use the + character to add a variable to another variable:
Example
String firstName = "John ";
String lastName = "Doe";
String fullName = firstName + lastName;
System.out.println(fullName);In Java, the + symbol has two meanings:
- For text (strings), it joins them together (called concatenation ).
- For numbers, it adds values together.
For numeric values, the + character works as a mathematical operator (notice that we use int (integer) variables here):
Example
int x = 5;
int y = 6;
System.out.println(x + y); // Print the value of x + yFrom the example above, here's what happens step by step:
- x stores the value 5
- y stores the value 6
- println() displays the result of x + y , which is 11
Mixing Text and Numbers
Be careful when combining text and numbers in the same line of code. Without parentheses, Java will treat the numbers as text after the first string:
Example
int x = 5;
int y = 6;
System.out.println("The sum is " + x + y); // Prints: The sum is 56
System.out.println("The sum is " + (x + y)); // Prints: The sum is 11Explanation
In the first line, Java combines "The sum is " with x , creating the string "The sum is 5" . Then y is added to that string, so it becomes "The sum is 56" .
In the second line, the parentheses make sure x + y is calculated first (resulting in 11 ), so the output is "The sum is 11" .