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Stacks.java
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57 lines (50 loc) · 1.7 KB
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/*
*A stack is exactly what it sounds like. An element gets added to 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 stacks have no fixed size, but with an array implementation it does.
*/
class Stack{
private int maxSize;
private int[] stackArray;
private int top;
public Stack(int size){ //Constructor
maxSize = size;
stackArray = new int[maxSize];
top = -1;
}
public void push(int value){ //Adds an element to the top of the stack
top++;
stackArray[top] = value;
}
public int pop(){ //Removes the top element of the stack and returns the value you've removed
return stackArray[top--];
}
public int peek(){ //Returns the element at the top of the stack
return stackArray[top];
}
public boolean isEmpty(){ //Returns true if the stack is empty
return(top == -1);
}
public boolean isFull(){ //Returns true if the stack is full
return(top+1 == maxSize);
}
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
}
}
//Example
public class Stacks{
public static void main(String args[]){
Stack myStack = new Stack(4); //Declare a stack of maximum size 4
//Populate the stack
myStack.push(5);
myStack.push(8);
myStack.push(2);
myStack.push(9);
System.out.println(myStack.isEmpty()); //will print false
System.out.println(myStack.isFull()); //will print true
System.out.println(myStack.peek()); //will print 9
System.out.println(myStack.pop()); //will print 9
System.out.println(myStack.peek()); // will print 2
}
}