Can I pass a primitive type by reference in Java?

Question

I would like to call a method which could potentially take on different versions, i.e. the same method for input parameters that are of type:

• boolean
• byte

Answer 1

While Java supports overloading, all parameters are passed by value, i.e. assigning a method argument is not visible to the caller.

From your code snippet, you are trying to return a value of different types. Since return types are not part of a method's signature, you can not overload with different return types. Therefore, the usual approach is:

int getIntValue() { ... }
byte getByteValue() { ... }

If this is actually a conversion, the standard naming is

int toInt() { ...}
byte toByte() { ... }

Answer 2

Primitives are not passed by references (or objects for that matter) so no you cannot.

int i = 1;
moo(i);
public void moo(int bah)
{
   bah = 3;
}
System.out.println(i);

Prints out 1

Answer 3

Sounds like you have a set of bits that you're parsing through. You should have it wrapped in an object, lets call that object a BitSet. You're iterating through the bits, so you'll have something like an Iterator<Bit>, and as you go you want to parse out bytes, ints, longs, etc... Right?

Then you'll have your class Parser, and it has methods on it like:

public byte readByte(Iterator<Bit> bitit) {
  //reads 8 bits, which moves the iterator forward 8 places, creates the byte, and returns it
}
public int readInt(Iterator<Bit> bitit) {
  //reads 32 bits, which moves the iterator forward 32 places, creates the int, and returns it
}

etc...

So after you call whichever method you need, you've extracted the value you want in a typesafe way (different return types for different methods), and the Iterator has been moved forward the correct number of positions, based on the type.

Is that what you're looking for?

Answer 4

Java is always pass-by-value. There is no pass-by-reference in Java. It's written in the specs!

Answer 5

Yes, please be more specific about what you want to achieve. From your description I suggest you have a look at Java generics where you could write something like this:

class SomeClass <GenericType> {
  GenericType val;  

  void setValue(GenericType val) {
     this.val = val;
  }

  GenericType getValue() {
     return val;
  }

  public static void main(String[] args) {
    SomeClass<Integer> myObj = new SomeClass<Integer>();
    myObj.setValue(5);
    System.out.println(myObj.getValue());

    SomeClass<String> myObj2 = new SomeClass<String>();
    myObj2.setValue("hello?!");
    System.out.println(myObj2.getValue());

  }

}

Answer 6

You can't. In Java parameters are always passed by value. If the parameter is a reference type, the reference is passed by value and you can modify it inside the method while with primitive types this is not possible.

You will need to create a wrapper type.