Following are examples of different types of variables in Java.

String

Alpha numeric characters.

String foo = "bar";
out.println(foo);

byte

numbers between -128 through 127. Uses less memory than short, int, and long. When a value is not defined, the default value is 0. In this example, 0 will be printed.

byte number;
out.println(number);

The specific value can be specified. In this example, 123 will be printed.

number = 123;
out.println(number);

short

numbers between -32768 and 32767. Uses more memory than byte, less memory than int and long. When a value is not defined, the default value is 0. In this example, 0 will be printed.

short number;
out.println(number);

The specific value can be specified. In this example, 12345 will be printed.

number = 12345;
out.println(number);

int

large numbers. Uses more memory than byte and short, less memory than long. When a value is not defined, the default value is 0. In this example, 0 will be printed.

int number;
out.println(number);

The specific value can be specified. In this example, 123456789 will be printed.

number = 123456789;
out.println(number);

long

very large numbers. Uses more memory than byte, short, and int. When a value is not defined, the default value is 0. In this example, 0 will be printed.

long number;
out.println(number);

The specific value can be specified. In this example, 1234567890123456789 will be printed.

bignumber = 1234567890123456789;
out.println(number);

float

floating point numbers. Do not use this for currency. Instead, use the java.math.BigDecimal class. When a value is not defined, the default value is 0.0. In this example, 0.0 will be printed.

float number;
out.println(number);

The specific value can be specified. In this example, 1.2 will be printed.

number = 1.2;
out.println(number);

double

floating point numbers. Do not use this for currency. Instead, use the java.math.BigDecimal class. When a value is not defined, the default value is 0.0. In this example, 0.0 will be printed.

double number;
out.println(number);

The specific value can be specified. In this example, 1.2 will be printed.

number = 1.2;
out.println(number);

boolean

contain a value of only true or false. The default value is false.

boolean result;
if (result == true) {
  out.println("result is true");
}
else {
  out.println("result is false");
}