Method Overloading with default param values

[Anjanesh Lekshminarayanan]

Hi

Why doesnt this method overloading work ?

public static String foo()
 {
        return foo(5, 10);
 }
 
public static String foo(byte a)
 {
        return foo(a, 10);
 }
 
public static String foo(byte a, byte b)
 {
        StringBuilder strList = new StringBuilder();
        //
        //
        //
        return strList.toString();
 }
 
public static void main(String[] args) throws Exception
 {
 }

I was trying to assign default values
(like public static String foo(byte a = 5, byte b = 10))
only to realize tha Java doesnt support default assignments.

I get

cannot find symbol
symbol  : method foo(byte,byte)

JDK 6

Thanks

[Jesper de Jong]

Are you sure that that's exactly the error you are getting? Because that would be strange. I compiled this small test program:

public class Main {
    public static String foo() {
        foo(5, 10);
    }
 
    public static String foo(byte a) {
        foo(a, 10);
    }
 
    public static String foo(byte a, byte b) {
        return String.format("[%d, %d]", a, b);
    }
 
    public static void main(String[] args) {
    }
}

And got the following errors:

Main.java:3: cannot find symbol
symbol  : method foo(int,int)
location: class Main
                foo(5, 10);
                ^
Main.java:7: cannot find symbol
symbol  : method foo(byte,int)
location: class Main
                foo(a, 10);
                ^
2 errors

Note that the compiler does not complain that it can't find foo(byte, byte) - it does complain that it can't find variants of this function that take an int parameter. That is because the literal numeric values are of type int, not byte. They are not automatically converted to byte.

You can either (1) cast the literals to byte, or (2) use int instead of byte in the method arguments.

// (1) Either cast the literals to byte:
foo((byte) 5, (byte) 10);
 
// (2) Change your foo(byte, byte) method to:
public static String foo(int a, int b) {
    // ...
}

[Anjanesh Lekshminarayanan]

Ah..Thanks.

Yes - you're right, I got

Main.java:3: cannot find symbol
symbol  : method foo(int,int)
location: class Main
        foo(5, 10);
        ^
Main.java:7: cannot find symbol
symbol  : method foo(byte,int)
location: class Main
        foo(a, 10);
        ^
2 errors

I wanted to use byte to save memory since I know the values are going to be from 1-50 or so.

So I got to typecast all literals manually ?

[Jesper de Jong]

Originally posted by Anjanesh Lekshminarayanan:
So I got to typecast all literals manually ?

If you explicitly want these to be interpreted as byte and not as int, yes.

There's one special case for byte in the Java language. When you declare a byte and you assign a literal value to it, you don't have to cast it.

byte value = 86;  // OK, no need for (byte) 86
 
byte value = 212;  // Error because 212 is outside the range -128...127 for byte

[Ernest Friedman-Hill]

Originally posted by Anjanesh Lekshminarayanan:

I wanted to use byte to save memory

Using byte-sized method parameters will not have any effect on memory usage. Using bytes as member variable may.