package com.thealgorithms.datastructures.stacks;
public class StackArray<T> implements Stack<T> {
private static final int DEFAULT_CAPACITY = 10;
private int maxSize;
private T[] stackArray;
private int top;
@SuppressWarnings("unchecked")
public StackArray() {
this(DEFAULT_CAPACITY);
}
@SuppressWarnings("unchecked")
public StackArray(int size) {
if (size <= 0) {
throw new IllegalArgumentException("Stack size must be greater than 0");
}
this.maxSize = size;
this.stackArray = (T[]) new Object[size];
this.top = -1;
}
@Override
public void push(T value) {
if (isFull()) {
resize(maxSize * 2);
}
stackArray[++top] = value;
}
@Override
public T pop() {
if (isEmpty()) {
throw new IllegalStateException("Stack is empty, cannot pop element");
}
T value = stackArray[top--];
if (top + 1 < maxSize / 4 && maxSize > DEFAULT_CAPACITY) {
resize(maxSize / 2);
}
return value;
}
@Override
public T peek() {
if (isEmpty()) {
throw new IllegalStateException("Stack is empty, cannot peek element");
}
return stackArray[top];
}
private void resize(int newSize) {
@SuppressWarnings("unchecked") T[] newArray = (T[]) new Object[newSize];
System.arraycopy(stackArray, 0, newArray, 0, top + 1);
stackArray = newArray;
maxSize = newSize;
}
public boolean isFull() {
return top + 1 == maxSize;
}
@Override
public boolean isEmpty() {
return top == -1;
}
@Override public void makeEmpty() {
top = -1;
}
@Override
public int size() {
return top + 1;
}
}