Getter-Setter and private variables [duplicate]

Question

If I can change the value of private variable through getter-returned reference then isn't it bypassing the setter method? Doesn't it defeat the purpose of getter-setter and private variables

public class Test{

private Dimension cannotBeChanged;

public Test(int height, int width)
{
    if(height!=3)
       cannotBeChanged.height = height;
    if(width!=3)
       cannotBeChanged.width  = width;
}

public Dimension getDimension()
{
    return cannotBeChanged;
}


public void setDimension(int height, int width)
{
    if(height!=3)
       cannotBeChanged.height = height;
    if(width!=3)
       cannotBeChanged.width  = width;    
} 

 public static void main(String [] args)
{
    Test testOne = new Test(5,5);
    Dimension testSecond = testOne.getDimension();
    testSecond.height = 3; //Changed height and width to unwanted values
    testSecond.width= 3;
}

Answer 1

Yes, It does. I have the following conclusion in getters and setters from the Clean Code book; you can use it if you really accept it.

1. Very evil: public fields.
2. Somewhat evil: Getters and setters where they're not required.
3. Good: Getters and setters only where they're really required - make the type expose "larger" behaviour which happens to use its state, rather than just treating the type as a repository of state to be manipulated by other types.

Answer 2

Programmer should devise the ways for external entities to touch the secured variables of his program.

1. Never create any setter for a secured property of your object. Only a getter can be provided.
2. Create setters only for those properties, which can change during the course of program.
3. Use setters if you want to apply certain restrictions on some properties e.g. apply invalid value checks, pre-population, logical analysis, populating another depending property, defensive copying etc
4. Getters/setters helps in maintaining the software entropy of a system. Read about software entropy.
5. Do not create getters/setters where it is not required as its leads to Boilerplate code.
6. Getters/setters helps in changing the underlying implementation for future Extensions of Programs e.g. Upgrading Logging libraries etc