Java Data Types

As the name suggests, data types specify the type of data that can be stored inside variables in Java.

Java is a statically-typed language. This means that all variables must be declared before they can be used.

int speed;

Here, speed is a variable, and the data type of the variable is int. The int data type determines that the speed variable can only contain integers.

There are 8 data types predefined in the Java programming language, known as primitive data types.

Summary of Primitive Data Types

1. Boolean Type

The boolean data type has two possible values: true or false. They are usually used for true/false conditions.

boolean isJavaFun = true;
boolean isFishTasty = false;
System.out.println(isJavaFun); // Outputs true
System.out.println(isFishTasty); // Outputs false

2. Byte Type

The byte data type can have values from -128 to 127 (8-bit signed two's complement integer). It is used to save memory in large arrays, where the memory savings actually matters.

byte myByte = 100;
System.out.println(myByte);

3. Short Type

The short data type can have values from -32768 to 32767 (16-bit signed two's complement integer).

short myShort = 5000;
System.out.println(myShort);

4. Int Type

The int data type is the default data type for integral values unless there is a problem with memory.

int myInt = 100000;
System.out.println(myInt);

5. Long Type

The long data type is used when you need a range of values wider than those provided by int.

Note: You must end the value with an "L".

long myLong = 15000000000L;
System.out.println(myLong);

6. Float Type

The float data type is a single-precision 32-bit floating-point. It should never be used for precise values such as currency.

Note: You must end the value with an "f".

float myFloat = 5.75f;
System.out.println(myFloat);

7. Double Type

The double data type is a double-precision 64-bit floating-point. It is the default type for decimal numbers.

double myDouble = 19.99d;
System.out.println(myDouble);

8. Char Type

The char data type is used to store a single character. The character must be surrounded by single quotes, like 'A' or 'c'.

char myGrade = 'B';
System.out.println(myGrade);

Alternatively, you can use ASCII values to display certain characters:

char myVar1 = 65, myVar2 = 66, myVar3 = 67;
System.out.println(myVar1); // A
System.out.println(myVar2); // B
System.out.println(myVar3); // C

Key Takeaways

• 8 Primitives: boolean, byte, short, int, long, float, double, char.
• Default Types: int is the default for whole numbers, double for decimals.
• Suffixes: Use L for long (e.g., 100L) and F for float (e.g., 3.14F).

Common Pitfalls

[!WARNING] Integer Division: Dividing two integers results in an integer (e.g., 5 / 2 = 2). Use 5.0 / 2 to get 2.5.

[!WARNING] Overflow: Storing a value larger than a type can handle (like putting 130 in a byte) causes overflow and unexpected negative numbers.

Challenge