Problem Description: How to implement stack ?

A stack is a data structure that uses the concept of last in first out (LIFO). It follows the concept of plate stack because the first entry in a plate stack is the last to be retrieved.

Solution
Following example shows how to implement stack by creating user defined push() method for entering elements and pop() method for retrieving elements from the stack.

public class MyStack { 

          private int maxSize; 

          private long[] stackArray; 

          private int top; 

          public MyStack(int s) { 

                    maxSize = s; 

                    stackArray = new long[maxSize]; 

                    top = -1; 

         }

         public void push(long j) {

                   stackArray[++top] = j; 

         } 

         public long pop() { 

                   return stackArray[top--]; 

         } 

         public long peek() { 

                   return stackArray[top]; 

         }

        public boolean isEmpty() { 

                   return (top == -1);

        } 

        public boolean isFull() { 

                   return (top == maxSize - 1); 

        } 

        public static void main(String[] args) { 

                  MyStack theStack = new MyStack(10); 

                  theStack.push(10); 

                  theStack.push(20); 

                  theStack.push(30); 

                  theStack.push(40); 

                  theStack.push(50); 

                  while (!theStack.isEmpty()) { 

                            long value = theStack.pop(); 

                            System.out.print(value); 

                            System.out.print(" "); 

                  } 

                 System.out.println(""); 

        } 

}