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  1. import java.util.ArrayList;
  2. import java.util.Arrays;
  3. import java.util.Scanner;
  4.  
  5. class Stack {
  6.  
  7.     private int pointer;
  8.     private int[] stack;
  9.     private int size;
  10.  
  11.  
  12.     public Stack() {
  13.         this(20);
  14.     }
  15.  
  16.     public Stack(int capacity) {
  17.             size = capacity;
  18.             stack = new int[size];
  19.             pointer = -1;
  20.     }
  21.  
  22.     public void push(int element) {
  23.         stack[++pointer] = element;
  24.     }
  25.  
  26.     public int pop() {
  27.         int i = stack[pointer];
  28.         stack[pointer--] = 0;
  29.         return i;
  30.     }
  31.  
  32.     public int back() {
  33.         return stack[pointer];
  34.     }
  35.  
  36.     public void clear() {
  37.         Arrays.fill(stack, 0);
  38.         pointer = -1;
  39.     }
  40.  
  41.     public boolean isEmpty() {
  42.         if (pointer < 0)
  43.             return true;
  44.         else
  45.             return false;
  46.     }
  47.  
  48.     public int size() {
  49.         return this.pointer + 1;
  50.     }
  51.  
  52.     public static void main(String[] args) {
  53.         Stack stack = new Stack();
  54.  
  55.         Scanner scanner = new Scanner(System.in);
  56.         System.out.println("enter your command");
  57.         String command = scanner.nextLine();
  58.  
  59.         while (!command.equals("exit")) {
  60.             if (command.matches("^push [0-9]")) {
  61.                 String[] comm = command.split(" ");
  62.                 stack.push(Integer.parseInt(comm[1]));
  63.                 System.out.println("OK");
  64.             } else if (command.equals("pop")) {
  65.                 if (stack.isEmpty()) {
  66.                     System.out.println("Error. Stack is empty");
  67.                 } else {
  68.                     System.out.println(stack.pop());
  69.                 }
  70.             } else if (command.equals("size")) {
  71.                 System.out.println(stack.size());
  72.             } else if (command.equals("back")) {
  73.                 if (stack.isEmpty()) {
  74.                     System.out.println("Error. Stack is empty");
  75.                 } else {
  76.                     System.out.println(stack.back());
  77.                 }
  78.             } else if (command.equals("clear")) {
  79.                 stack.clear();
  80.                 System.out.println("OK");
  81.             } else {
  82.                 System.out.println("Command doesn't exist");
  83.             }
  84.             command = scanner.nextLine();
  85.         }
  86.         System.out.println("bye");
  87.  
  88.     }
  89. }
  90.  
Success #stdin #stdout 0.06s 711680KB
comments (?)
stdin
copy 
push 8
push 4
size
pop
back
push 8
push 7
clear
size
exit
stdout
copy 
enter your command
OK
OK
2
4
8
OK
OK
OK
0
bye
https://ideone.com/MlYQ2D
final stack
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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