Variable types

1. Declaring variables

Let's take another look at how to create variables.

To create a variable, you need to write the following command: type name;.

Examples:

String s;

int x;

int a, b, c;
int d;

There are also restrictions on the name of a variable. On the one hand, it can be anything. But on the other hand, it cannot contain spaces or special characters such as +, -, etc. It is best to use only Latin letters and numerals in a variable's name.

Note that in Java it matters whether you write uppercase or lowercase letters. int a is not the same as Int a.

By the way, in Java you can create a variable and simultaneously assign a value to it. This saves time and space:

int a = 5;

int a;
a = 5;

int b = 6;

int b;
b = 6;

int c = 7;

int c;
c = 7;

int d = c + 1;

int d;
d = c + 1;

String s = "I'm Amigo";

String s;
s = "I'm Amigo";

That way is a lot more compact and clear.

Well, now that we've figured out how to create variables, let's get acquainted with the two most frequently used types in the Java language. They are int (integers) and String (text/strings).

2. The int type

An int variable can store integers. You can perform various operations (addition, subtraction, multiplication, division, and others) on int variables. Examples:

int x = 1;
int y = x*2;
int z = 5*y*y + 2*y + 3;

int a = 5;
int b = 1;
int c = (a-b) * (a+b);

int a = 64;
int b = a/8;
int c = b/4;
int d = c*3;

3. The String type

The String type lets you store lines of text, also known as strings.

To assign a string in Java, you need to write the text of the string inside quotation marks. Example:

String s = "Amigo";

String s = "123";

String s = "Bond 007";

Looks easy, right? If so, then here's another interesting fact.

In Java, you can join strings together with a plus sign (+). Example:

String s = "Amigo" + " is the best";

String s = "";

int x = 333;
String s = "Amigo" + x;

Notice that in the last example we concatenated a string and a number. Everything is simple here too: the number is converted to a string, and then the two strings are glued together. When concatenating strings and numbers, you always end up with a string.

4. Displaying a variable on the screen

It seems that everything is so obvious and simple. Then maybe you can guess right away which command you can use to display a variable on the screen?

Indeed, everything is simple. To display something on the screen, we use the System.out.println() command. Whatever we want to display, we pass in as an argument.

System.out.println("Amigo");

Amigo

System.out.println("Ami" + "go");

Amigo

String s = "Amigo";
System.out.println(s);

Amigo

String s = "Am";
System.out.println(s + "igo");

Amigo

Hopefully this is a little clearer now. Now we're going to check whether you understood everything correctly. Practice is the litmus test: only practice can help you know whether you have understood everything well.

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Task

New Java Syntax, level 1, lesson 4

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Kind words for the teacher

Write a program that displays "Ellie is very smart" 5 times. Each time, on a new line. Example output: Ellie is very smart Ellie is very smart Ellie is very smart Ellie is very smart Ellie is very smart

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Task

New Java Syntax, level 1, lesson 4

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My young friend

It's currently 3126. My friend was born 8 years ago. Write a program that displays my friend's birth year.

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Task

New Java Syntax, level 1, lesson 4

Locked

Declare variables

Write a program that declares the following variables in the main method: String name, int age, and String city. Note: "Declaring a variable" is the same thing as "creating a variable".

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