Type

byte, short, int, long (integers)

 byte b = 1; // bytes are 8 bits long, [-128, 127]
 short s = 10; // shorts are 16 bits long, [-32,768, 32,767]
 int i = 20; // ints are 32 bits long, [-2^31, 2^31)
 long l = 30; // longs are 64 bits long, [-2^63, 2^63)
 // all are of 2's complement

float, double (floating numbers)

 float f = 10f; // single-precision 32-bit IEEE 754 floating point 
 double d = 20.0; // double-precision 64-bit IEEE 754 floating point

String, char (Text)

 String s = "This is a string";
 char c = 'G'; // this is a character
 // char can only be one letter long and uses single quotes

boolean (true and false)

 boolean tf = true; // booleans designtes true or false

array ( T[] where T is the defining type of the array)

// creates an int array of size five filled with default values
// in this case the default value of an int is 0
int[] arr = new int[5]; 

int[] arr is [0, 0, 0, 0, 0] To access a value in an array, an index is required.

All array indices start at 0 and go up to the length of the array - 1

int[] arr = new int[5];
  
arr[0] = 1;
arr[1] = 2;
arr[2] = 3;
arr[3] = 4;
arr[4] = 5;

System.out.println(Arrays.toString(arr)); // prints out the list in readable form, this is imported from java.util.Arrays

int[] arr is now [ 1, 2, 3, 4, 5]

You can create an array of any type, just use [] after the type and it will become an array. i.e. int[] double[] byte[] String[] char[] boolean[]

reference: Basic Types and Arrays and Strings

All of the above types are known as primitives, except String. Primitive types begin with a lowercase letter and are the types you’d expect a language to handle intuitively. However, they don’t have all the features of complex types like String and ArrayList, which you’ll learn about later. For this reason, Java has a workaround known as auto-encapsulation where it will automatically treat primitives like int as complex wrappers like Integer, and vice versa, depending on context.