# Java: Reverse the elements of a stack

## Java Stack: Exercise-4 with Solution

Write a Java program to reverse the elements of a stack.

Sample Solution:

Java Code:

``````import java.util.Scanner;
public class Stack {
private int[] arr;
private int top;

// Constructor to initialize the stack
public Stack(int size) {
arr = new int[size];
top = -1;
}

// Method to push an element onto the stack
public void push(int num) {
if (top == arr.length - 1) {
System.out.println("Stack is full");
} else {
top++;
arr[top] = num;
}
}

// Method to pop an element from the stack
public int pop() {
if (top == -1) {
System.out.println("Stack Underflow");
return -1;
} else {
int poppedElement = arr[top];
top--;
return poppedElement;
}
}

// Method to get the top element of the stack
public int peek() {
if (top == -1) {
System.out.println("Stack is empty");
return -1;
} else {
return arr[top];
}
}

// Method to check if the stack is empty
public boolean isEmpty() {
}

public void reverse() {
if (top == -1) {
System.out.println("Stack is empty");
return;
}

int[] reversedArray = new int[arr.length];
int index = 0;

while (!isEmpty()) {
int temp = pop();
reversedArray[index++] = temp;
}

for (int i = 0; i < index; i++) {
push(reversedArray[i]);
}
}
public void display() {
if (top == -1) {
System.out.println("Stack is empty");
} else {
System.out.print("Stack elements: ");
for (int i = top; i >= 0; i--) {
System.out.print(arr[i] + " ");
}
System.out.println();
}
}

public static void main(String[] args) {
System.out.println("Initialize a stack:");
Stack stack = new Stack(10);
System.out.println("\nInput some elements on the stack:");
stack.push(1);
stack.push(3);
stack.push(2);
stack.push(0);
stack.push(7);
stack.push(5);
stack.display();
System.out.println("\nReverse the elements of the said stack:");
stack.reverse();
stack.display();
System.out.println("\nInput two more elements on the stack:");
stack.push(9);
stack.push(10);
stack.display();
System.out.println("\nReverse the elements of the said stack:");
stack.reverse();
stack.display();
}
}
```
```

Sample Output:

```Initialize a stack:

Input some elements on the stack:
Stack elements: 5 7 0 2 3 1

Reverse the elements of the said stack:
Stack elements: 1 3 2 0 7 5

Input two more elements on the stack:
Stack elements: 10 9 1 3 2 0 7 5

Reverse the elements of the said stack:
Stack elements: 5 7 0 2 3 1 9 10

```

Flowchart:

Live Demo:

Java Code Editor:

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Java Stack Previous: Sort the elements of a stack in descending order.
Java Stack Exercises Next: Find the maximum and minimum elements in a stack.

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