Question

Java has a class for a stack. It is java.util.Stack. Let us make use of this class.

Step 1: Create a project. Name the project MyStk. This will result in the creation of the main class called MyStk if you are using Netbeans IDE with relevant default settings unchanged. If comments are excluded you should see the following in the code editor after creating the project.

package mystk;
public class MyStk {
public static void main(String[ ] args){
}
}
Step 2: Now, import the class java.util.Stack to your application by adding the statement for importing (import java.util.Stack;) as shown below. package mystk;

import java.util.Stack;//recently added public
class MyStk {
public static void main(String[ ] args){
}
}
Step 3: Create an object of java.util.Stack in public static void main(String[ ] args). Name the object stkObj. The code should appear as shown below.

package mystk;
import java.util.Stack;
public class MyStk {
public static void main(String[ ] args){
Stack stkObj = new Stack();//recently added
}
}
Step 4: Push objects onto the stack (stkObj) by making use of the void push(Object e) method found in java.util.Stack. Now, your code should appear as shown below.

import java.util.Stack;
public class MyStk {
public static void main(String[ ] args){
Stack stkObj = new Stack();
stkObj.push(“Dune”); //recently added
stkObj.push(“Jane”); //recently added
stkObj.push(“Pinky”); //recently added
}
}

Step 5: Write code to display the contents of stkObj (the stack object) after pushing objects onto it. Your code should appear as shown below.

import java.util.Stack;
public class MyStk {
public static void main(String[ ] args){
Stack stkObj = new Stack();
stkObj.push(“Dune”);
stkObj.push(“Jane”);
stkObj.push(“Pinky”);
System.out.println(“Stack after pushing: ”+stkObj);//recently added
}
}
Step 5a: Run your application and expect the following display. Stack after pushing: [Dune, Jane, Pinky]

Step 6: Pop an object off the stack (stkObj) by making use of the void pop( ) method found in java.util.Stack. Now, your code should appear as shown below.

package mystk;
import java.util.Stack;
public class MyStk {
public static void main(String[ ] args){
Stack stkObj = new Stack();
stkObj.push(“Dune”); //recently added
stkObj.push(“Jane”); //recently added
stkObj.push(“Pinky”); //recently added
System.out.println(“Stack after pushing: ”+stkObj);
stkObj.pop();//recently added
}
}

Step 7: Write code to display the contents of stkObj (the stack object) after popping an object off stkObj. Your code should appear as shown below.

package mystk;
import java.util.Stack;
public class MyStk {
public static void main(String[ ] args){
Stack stkObj = new Stack();
stkObj.push(“Dune”);
stkObj.push(“Jane”);
stkObj.push(“Pinky”);
System.out.println(“Stack after pushing: ”+stkObj);
stkObj.pop();
System.out.println(“Stack after popping: ”+stkObj); //recently added
}
}

Step 7a: Run your application and expect the following display.

Stack after pushing: [Dune, Jane, Pinky]

Stack after popping: [Dune, Jane]

Answer 1

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CODE

TILL STEP 5

import java.util.Stack;

public class MyStk {

   @SuppressWarnings("unchecked")
   public static void main(String[] args) {
       @SuppressWarnings("rawtypes")

       Stack stkObj = new Stack();
       stkObj.push("Dune");
       stkObj.push("Jane");
       stkObj.push("Pinky");
       System.out.println("Stack after pushing: "+stkObj);
   }

}

OUTPUT in CONSOLE

CODE in EDITOR

AFTER STEP 6

import java.util.Stack;

public class MyStk {

   @SuppressWarnings("unchecked")
   public static void main(String[] args) {
       @SuppressWarnings("rawtypes")

       Stack stkObj = new Stack();
       stkObj.push("Dune");
       stkObj.push("Jane");
       stkObj.push("Pinky");
       System.out.println("Stack after pushing: "+stkObj);

       stkObj.pop();
       System.out.println("Stack after popping: "+stkObj);
   }

}

OUTPUT in CONSOLE

CODE in EDITOR

Explanation

ENTIRE CODE

// importing stack class
import java.util.Stack;

// MyStk class
public class MyStk {

   // Main method
   @SuppressWarnings("unchecked")
   public static void main(String[] args) {
       @SuppressWarnings("rawtypes")

       // Creating stack class object
       Stack stkObj = new Stack();
       // stkObj = []

       // adding value to stack
       stkObj.push("Dune");
       // stkObj = ["Dune"]
       // top element = "Dune"

       // adding value to stack
       stkObj.push("Jane");
       // stkObj = ["Dune","Jane"]
       // top element = "Jane"

       // adding value to stack
       stkObj.push("Pinky");
       // stkObj = ["Dune","Jane","Pinky"]
       // top element = "Pinky"

       // Printing stack
       System.out.println("Stack after pushing: "+stkObj);

       // Popping top element from stack
       // This will remove top element from stack
       stkObj.pop();
       // stkObj = ["Dune","Jane"]
       // top element = "Jane"

       // printing stack after above operations
       System.out.println("Stack after popping: "+stkObj);
   }

}

OUTPUT in CONSOLE

CODE in EDITOR

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