Stack Implementation Java Code 


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package LinearDS;

public class ImplementStack {

 public static void main(String[] args) {
  Stack obj = new Stack(4);
  obj.push("1");
  System.out.println(obj.peek());
  obj.push("2");
  System.out.println(obj.peek());
  obj.push("3");
  System.out.println(obj.peek());
  obj.push("4");
  System.out.println(obj.peek());
  obj.push("5");

  //System.out.println(obj.peek());
 }

}

class Stack {
 int maxsize;
 int top;
 String[] arr;

////////////////////////////////////////constructor
 public  Stack(int n) {
  maxsize = n;
  arr = new String[maxsize];
  top = 0;
 }

 ////////////////////////////////////EMPTY
 public boolean empty() {
  if (top == 0) {
   return true;
  } else
   return false;
 }


 ///////////////////////////////////PUSH
 public void push(String str) {
  if (top < maxsize) {
   arr[top] = str;
   top++;
  }
  else {
   System.out.println("stack overflow");
  }

 }

 //////////////////////////////////// POP
 public String pop() {
  if ( !this.empty()) {
   String temp = this.peek();
   arr[top - 1] = null;
   top--;
   return temp;
  } else {
   return null;
  }
 }


 //////////////////////////////////////PEEK
 public String peek() 
  if (top > 0) {
   return arr[top - 1];
  } else {
   return null;
  }
 }

}

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