The default value for an integer primitive is zero. : Integer « Java Source And Data Type « SCJP

public class MainClass {
  static int i;

  public static void main(String[] argv) {

    System.out.println(i);
  }
}

1.9.Integer
	1.9.1.	Ranges of the Integral Primitive Types
	1.9.2.	An integer literal is a value specified in the program source.
	1.9.3.	The default value for an integer primitive is zero.
	1.9.4.	Default Integral literal is decimal
	1.9.5.	Octal integer literal (To indicate octal, prefix the literal with 0 (zero))
	1.9.6.	Hexadecimal integer literal (To indicate hexadecimal, prefix the literal with 0x or 0X)
	1.9.7.	octal, decimal, and hexadecimal may be specified as long by placing a suffix of L or l after the number
	1.9.8.	out of range for short primitive
	1.9.9.	Assign a primitive variable using a literal or the result of an expression.
	1.9.10.	A literal integer is always an int, compiler automatically narrows the literal value to a byte
	1.9.11.	Add two bytes together and you'll get an int.
	1.9.12.	Integer literals are assumed to be of type int unless the letter L or l is appended.
	1.9.13.	Division by zero in integer arithmetic produces a runtime ArithmeticException.