JavaAlgorithms/DataStructures/Stacks/StackArray.java

152 lines
4.0 KiB
Java
Raw Normal View History

/**
* This class implements a Stack using a regular array.
2019-01-06 08:56:51 +08:00
* <p>
* A stack is exactly what it sounds like. An element gets added to the top of
* the stack and only the element on the top may be removed. This is an example
* of an array implementation of a Stack. So an element can only be added/removed
* from the end of the array. In theory stack have no fixed size, but with an
* array implementation it does.
*
* @author Unknown
*/
2019-01-06 08:56:51 +08:00
public class StackArray {
/**
* Main method
*
* @param args Command line arguments
*/
public static void main(String[] args) {
// Declare a stack of maximum size 4
StackArray myStackArray = new StackArray(4);
// Populate the stack
myStackArray.push(5);
myStackArray.push(8);
myStackArray.push(2);
myStackArray.push(9);
System.out.println("*********************Stack Array Implementation*********************");
System.out.println(myStackArray.isEmpty()); // will print false
System.out.println(myStackArray.isFull()); // will print true
System.out.println(myStackArray.peek()); // will print 9
System.out.println(myStackArray.pop()); // will print 9
System.out.println(myStackArray.peek()); // will print 2
}
/**
* The max size of the Stack
*/
private int maxSize;
/**
* The array representation of the Stack
*/
private int[] stackArray;
/**
* The top of the stack
*/
private int top;
/**
* Constructor
*
* @param size Size of the Stack
*/
public StackArray(int size) {
maxSize = size;
stackArray = new int[maxSize];
top = -1;
}
2019-01-06 08:56:51 +08:00
/**
* Adds an element to the top of the stack
*
* @param value The element added
*/
public void push(int value) {
if (!isFull()) { // Checks for a full stack
top++;
stackArray[top] = value;
} else {
resize(maxSize * 2);
push(value); // don't forget push after resizing
}
}
2019-01-06 08:56:51 +08:00
/**
* Removes the top element of the stack and returns the value you've removed
*
* @return value popped off the Stack
*/
public int pop() {
if (!isEmpty()) { // Checks for an empty stack
return stackArray[top--];
}
if (top < maxSize / 4) {
resize(maxSize / 2);
return pop();// don't forget pop after resizing
} else {
System.out.println("The stack is already empty");
return -1;
}
}
2019-01-06 08:56:51 +08:00
/**
* Returns the element at the top of the stack
*
* @return element at the top of the stack
*/
public int peek() {
if (!isEmpty()) { // Checks for an empty stack
return stackArray[top];
} else {
System.out.println("The stack is empty, cant peek");
return -1;
}
}
2019-01-06 08:56:51 +08:00
private void resize(int newSize) {
int[] transferArray = new int[newSize];
for (int i = 0; i < stackArray.length; i++) {
transferArray[i] = stackArray[i];
}
2019-09-03 11:23:01 +08:00
// This reference change might be nice in here
stackArray = transferArray;
2019-01-06 08:56:51 +08:00
maxSize = newSize;
}
/**
* Returns true if the stack is empty
*
* @return true if the stack is empty
*/
public boolean isEmpty() {
return (top == -1);
}
2019-01-06 08:56:51 +08:00
/**
* Returns true if the stack is full
*
* @return true if the stack is full
*/
public boolean isFull() {
return (top + 1 == maxSize);
}
2019-01-06 08:56:51 +08:00
/**
* Deletes everything in the Stack
* <p>
* Doesn't delete elements in the array
* but if you call push method after calling
* makeEmpty it will overwrite previous
* values
*/
public void makeEmpty() { // Doesn't delete elements in the array but if you call
top = -1; // push method after calling makeEmpty it will overwrite previous values
}
2019-01-06 08:56:51 +08:00
}