I want to create a fixed-size stack and truncate the stack when is full. For this already exists a approach in Creating a fixed-size Stack, but I do not want to implement a class.
It is possible to do something like this?
Stack<String> stack = new Stack<String>(){ private static final long serialVersionUID = 1L; public String push(String item) { if (this.size() == FIXED_SIZE) { //truncate() } return super.push(item); } }; And the rest of the stack methods remain the same?
So this is what I found in the documentation. I did not use or tested it. So I am not sure how this would work out. Because removeElementAt() is inherited from Vector class, and I am hoping that removeElementAt(0), will still remove the element at the bottom.
Stack<String> stack = new Stack<String>(){ private static final long serialVersionUID = 1L; public String push(String item) { if (this.size() == FIXED_SIZE) { this.removeElementAt(0); } return super.push(item); } }; And also I am assuming that, what you meant by truncate is to remove the first-in element currently in the list, if you just want to reject the new coming element, you can just return null.
How about something like this:
Public class TruncatedStack<T> extends FixedStack<T> { private static final long serialVersionUID = 1L; @Override public String push(String item) { if (this.top == size) { this.top = -1; return super.push(item); } } Wrote this off the top of my head (untested). As mentioned in the comments, a fixed size stack is simply an array with a counter to keep track of the top.
public class FixedSizeStack { int top, numElements; int[] baseArray; public FixedSizeStack(int maxSize) { top = 0; numElements = 0; baseArray = new int[maxSize]; } public void push(int num) { baseArray[top] = num; top = (top+1) % baseArray.length; numElements++; } public int pop(int num) { if(numElements == 0) return null; //or throw exception--you've removed too many elements! numElements--; top = (top == 0) ? (baseArray.length - 1) : (top - 1); return baseArray[top]; } } Yep, you are almost exactly right. You just need to do a this.remove(0) and then you're done.
Stack<String> stack = new Stack<String>(){ @Override public String push(String item) { if (this.size() == FIXED_SIZE) { this.remove(0) } return super.push(item); } }; 