Not sure how to use protected method in arraylisy

Question

Hi,
Im wondering how to use the removeRange method in java arraylist, its a protected method which returns void.
http://java.sun.com/j2se/1.3/docs/api/java/util/ArrayList.html#removeRange(int,%20int)
So if my class extends Arraylist i should be able to call the method but the compiler states that it still has protected access in arraylist. Does this mean im still overriding the method in arraylist ? A little explanation of whats happeneing would be appreciated as much as an answer
thanks

Answer 1

In this codefinal class myClass extends java.util.ArrayList {
    private ArrayList array = new ArrayList();
    public myClass(ArrayList ary){
        for(int i=0;i<7;i++) {
            array.add(ary.get(i));
        ary.removeRange(0,7)
}You are defining a class called myClass which extends ArrayList.
You have a member variable called array which is an ArrayList
You have a constructor which takes a parameter called ary which is an ArrayList
Since ary is an ArrayList, you cannot call it's removeRange() method unless myClass is in the java.util package. Do not put your class in the java.util package.
It seems like what you want to do is to move the items in one ArrayList to another ArrayList rather than copying them. I wrote a program to do this. Here it isimport java.util.*;
public class Test3 {
  public static void main(String[] args) {
    MyClass myClass = new MyClass();
    for (int i=0; i<5; i++) myClass.add("Item-"+i);
    System.out.println("------ myClass loaded -------");
    for (int i=0; i<myClass.size(); i++) System.out.println(myClass.get(i));
    MyClass newClass = new MyClass(myClass);
    System.out.println("------ newClass created -------");
    for (int i=0; i<newClass.size(); i++) System.out.println(newClass.get(i));
    System.out.println("------ myClass now contains -------");
    for (int i=0; i<myClass.size(); i++) System.out.println(myClass.get(i));
class MyClass extends java.util.ArrayList {
    public MyClass() {}
    public MyClass(MyClass ary){
        for(int i=0;i<ary.size();i++) add(ary.get(i));
        ary.removeRange(0,ary.size());
}You should notice now that I don't create an ArrayList anywhere. Everything is a MyClass. By the way, class names are normally capitalized, variable names are not. Hence this line
MyClass myClass = new MyClass();
In the code above I create an empty MyClass and then populate it with 5 items and then print that list. Then I create a new MyClass using the constructor which takes a MyClass parameter. This copies the items from the parameter list into the newly created MyClass (which is an ArrayList) and then removes the items from the MyClass passed as a parameter. Back in the main() method, I then print the contents of the two MyClass objects.
One thing which may be a little confusing is this line.
for(int i=0;i<ary.size();i++) add(ary.get(i));
the add() call doesn't refer to anything. What it really refers to is the newly created MyClass object which this constructor is building. This newly created object is the 'this' object. So the line above could be rewritten as
for(int i=0;i<ary.size();i++) this.add(ary.get(i));
Hopefully this helps a little. The problems you seem to be having are associated with object oriented concepts. You might try reading this
http://sepwww.stanford.edu/sep/josman/oop/oop1.htm