Parameter Use

[Bill Gorder]

I am studying for the SCJP. Please take the following code snippet.

 package com.test;

public class ParameterTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		int a = 0;
		final int b = 1;
		int[] c = {2};
		final int[] d = {3};
		useArgs(a,b,c,d);
		System.out.println(d[0]);  //outputs 4
	}
	static void useArgs(final int a, int b, final int[] c, int[] d){
		a++;  // cannot do this
		b++;
		b = a;
		c[0]++;
		d[0]++;
		c = d; // cannot do this
	}

}
   

Now I have no problem with lines I have commented, as it makes sense to me. What does not make sense to me is why d[0]++ or c[0]++ works.

c[0]++ --> seems to me this changes the value of final int[] c

since arrays are passed as reference d[0]++ seems like it changes the value of final int[] d = {3}; in the main method.

Is it only the memory address pointing to the array object that cannot be changed or reassigned? For some reason I figured that the values within the array were also unchangeable.

Can somebody please clarify for me?

Thanks,

[Henry Wong]

Bill Gorder wrote:
Is it only the memory address pointing to the array object that cannot be changed or reassigned? For some reason I figured that the values within the array were also unchangeable.

No. When declaring a final variable, only the variable is not changeable. And in your example, the variable is a array reference. The reference can't be changed, but the array can be changed.

Henry

[Bill Gorder]

OK thanks for clearing that up for me Henry.