Question on Dan's Mock

[Murtuza Akhtari]

Question 19
class JSC205 {
  static int m1(int i) {return i;}     // 1
  static void m2(int i) {return i;}    // 2
  static int m3(int i) {return;}       // 3
  public static void main(String[] args) {
    System.out.print(""+m1(1)+m2(2)+m3(3)); // 4
}}
 
What is the result of attempting to compile and run the program? 
 
a.  Prints: 123 
b.  Prints: 6 
c.  Compile-time error at 1. 
d.  Compile-time error at 2. 
e.  Compile-time error at 3. 
f.  Compile-time error at 4. 

Answers : d,e,f

I understand the d and the e...but why is it a compiler error at line 4
Also the explanation to the answer is as follows:

At line 2, the statement, "return i;", contains the expression, i. The enclosing method, m2, is declared void. The return statement generates a compile-time error, because it contains an expression. At line 3, the statement, "return;", does not contain an expression. The enclosing method, m3, is declared with the result type, int. The return statement generates a compile-time error, because it does not contain an expression that produces a value that is assignable to the declared result type.

Thanks
[ August 14, 2004: Message edited by: Murtuza Akhtari ]

[Francis Siu]

hi Murtuza Akhtari

The enclosing method, m3, is declared with the result type, int. The return statement generates a compile-time error, because it does not contain an expression that produces a value that is assignable to the declared result type.

I can explain more aove statement, m3 is declered as a method and it will return an integer after invoked, but please notice the method body, it does not produce a value { return;} that matches the return type of method static int m3(....).... So, compile-time error occured.

[Dan Chisholm]

Murtuza,

At line 4, the print statement attempts to print the return values of the methods, but method m2 has a void return type.