Remove Stacks.java which has been replaced by two new files
StackArray.java & StackArrayList.java
This commit is contained in:
Hayder Hassan
parent
787a9fa0ca
commit
29b7ad43d1
@ -1,240 +0,0 @@
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import java.util.ArrayList;
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/**
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* This class implements a Stack using two different implementations.
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* Stack is used with a regular array and Stack2 uses an ArrayList.
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*
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* A stack is exactly what it sounds like. An element gets added to the top of
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* the stack and only the element on the top may be removed. This is an example
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* of an array implementation of a Stack. So an element can only be added/removed
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* from the end of the array. In theory stack have no fixed size, but with an
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* array implementation it does.
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*
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* @author Unknown
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*
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*/
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class Stack{
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/** The max size of the Stack */
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private int maxSize;
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/** The array representation of the Stack */
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private int[] stackArray;
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/** The top of the stack */
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private int top;
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/**
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* Constructor
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*
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* @param size Size of the Stack
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*/
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public Stack(int size){
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maxSize = size;
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stackArray = new int[maxSize];
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top = -1;
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}
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/**
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* Adds an element to the top of the stack
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*
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* @param value The element added
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*/
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public void push(int value){
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if(!isFull()){ //Checks for a full stack
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top++;
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stackArray[top] = value;
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}else{
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resize(maxSize*2);
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push(value);// don't forget push after resizing
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}
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}
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/**
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* Removes the top element of the stack and returns the value you've removed
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*
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* @return value popped off the Stack
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*/
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public int pop(){
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if(!isEmpty()){ //Checks for an empty stack
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return stackArray[top--];
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}
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if(top < maxSize/4){
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resize(maxSize/2);
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return pop();// don't forget pop after resizing
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}
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else{
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System.out.println("The stack is already empty");
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return -1;
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}
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}
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/**
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* Returns the element at the top of the stack
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*
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* @return element at the top of the stack
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*/
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public int peek(){
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if(!isEmpty()){ //Checks for an empty stack
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return stackArray[top];
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}else{
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System.out.println("The stack is empty, cant peek");
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return -1;
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}
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}
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private void resize(int newSize){
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//private int[] transferArray = new int[newSize]; we can't put modifires here !
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int[] transferArray = new int[newSize];
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//for(int i = 0; i < stackArray.length(); i++){ the length isn't a method .
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for(int i = 0; i < stackArray.length; i++){
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transferArray[i] = stackArray[i];
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stackArray = transferArray;
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}
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maxSize = newSize;
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}
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/**
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* Returns true if the stack is empty
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*
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* @return true if the stack is empty
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*/
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public boolean isEmpty(){
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return(top == -1);
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}
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/**
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* Returns true if the stack is full
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*
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* @return true if the stack is full
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*/
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public boolean isFull(){
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return(top+1 == maxSize);
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}
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/**
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* Deletes everything in the Stack
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*
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* Doesn't delete elements in the array
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* but if you call push method after calling
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* makeEmpty it will overwrite previous
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* values
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*/
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public void makeEmpty(){ //Doesn't delete elements in the array but if you call
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top = -1; //push method after calling makeEmpty it will overwrite previous values
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}
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}
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/**
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* This is an ArrayList Implementation of stack, Where size is not
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* a problem we can extend the stack as much as we want.
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*
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* @author Unknown
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*
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*/
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class Stack2{
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/** ArrayList representation of the stack */
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ArrayList<Integer> stackList;
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/**
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* Constructor
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*/
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Stack2(){
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stackList=new ArrayList<>();
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}
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/**
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* Adds value to the end of list which
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* is the top for stack
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*
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* @param value value to be added
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*/
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void push(int value){
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stackList.add(value);
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}
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/**
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* Pops last element of list which is indeed
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* the top for Stack
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*
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* @return Element popped
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*/
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int pop(){
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if(!isEmpty()){ // checks for an empty Stack
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int popValue=stackList.get(stackList.size()-1);
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stackList.remove(stackList.size()-1); //removes the poped element from the list
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return popValue;
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}
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else{
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System.out.print("The stack is already empty ");
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return -1;
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}
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}
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/**
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* Checks for empty Stack
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*
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* @return true if stack is empty
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*/
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boolean isEmpty(){
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if(stackList.isEmpty())
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return true;
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else return false;
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}
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/**
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* Top element of stack
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*
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* @return top element of stack
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*/
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int peek(){
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return stackList.get(stackList.size()-1);
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}
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}
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/**
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* This class implements the Stack and Stack2 created above
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*
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* @author Unknown
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*
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*/
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public class Stacks{
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/**
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* Main method
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*
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* @param args Command line arguments
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*/
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public static void main(String args[]){
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Stack myStack = new Stack(4); //Declare a stack of maximum size 4
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//Populate the stack
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myStack.push(5);
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myStack.push(8);
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myStack.push(2);
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myStack.push(9);
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System.out.println("*********************Stack Array Implementation*********************");
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System.out.println(myStack.isEmpty()); //will print false
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System.out.println(myStack.isFull()); //will print true
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System.out.println(myStack.peek()); //will print 9
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System.out.println(myStack.pop()); //will print 9
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System.out.println(myStack.peek()); // will print 2
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Stack2 myStack2 = new Stack2(); //Declare a stack of maximum size 4
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//Populate the stack
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myStack2.push(5);
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myStack2.push(8);
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myStack2.push(2);
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myStack2.push(9);
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System.out.println("*********************Stack List Implementation*********************");
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System.out.println(myStack2.isEmpty()); //will print false
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System.out.println(myStack2.peek()); //will print 9
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System.out.println(myStack2.pop()); //will print 9
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System.out.println(myStack2.peek()); // will print 2
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System.out.println(myStack2.pop()); //will print 2
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}
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}
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