In addition, a narrowing primitive conversion may be used if all of the following conditions are satisfied:

• The expression is a constant expression of type int.
  
• The type of the variable is byte, short, or char.
  
• The value of the expression (which is known at compile time, because it is a constant expression) is representable in the type of the variable.

That's the case here, so the compiler performs a narrowing conversion without a cast.

To see that the default is int, try this:

public class Test {
  static void method(byte b) {
    System.out.println(b + " is a byte!");
  }
  static void method(short s) {
    System.out.println(s + " is a short!");
  }
  static void method(int i) {
    System.out.println(i + " is an int!");
  }
  static void method(long l) {
    System.out.println(l + " is a long!");
  }
  public static void main(String[] args) {
    method(1);
  }
}