There were errors. Please fix and resubmit. See below for more details. === Compilation test... > Driver_prj0.java ... file not found >> aborting all tests 

import java.util.Scanner;

import java.util.Stack;

class Driver_prj0 {

/* main

* parameters:

* args -- the array of command line argument values

* return value: nothing

*

* PUT YOUR COMMENTS FOR THIS FUNCTION HERE

*/

public static void main(String[] args) {

// Here we initialize the scaner variable to read lines of input

Scanner input = new Scanner(System.in);

String line;

// the callStack is used for storing the names of functions that have been

// called and not yet returned

//Adding some elements to stack for testing

Stack callStack = new Stack();

callStack.push("F1");

callStack.push("F2");

callStack.push("F3");

// Each time we go through this while loop, we read a line of input.

// The function hasNext() returns a boolean, which is checked by the while

// condition. If System.in has reached the end of the file, it will return

// false and the loop will exit. Otherwise, it will return true and the

// loop will continue.

int lineNumber = 0;

int maximum_depth = 0;

int flag = 0;

while (input.hasNext()) {

line = input.nextLine();

lineNumber++;

System.out.println(line);

// PUT YOUR CODE HERE

if(callStack.empty()) {

System.out.println("Invalid Trace at line "+lineNumber);

System.out.println("Returning from "+line+" which was not called");

flag = 1;

break;

}

if(!(line.equals((String)callStack.peek()))) {

System.out.println("Invalid Trace at line "+lineNumber);

System.out.println("Returning from "+line+" instead of "+callStack.peek());

flag = 1;

break;

}

callStack.pop();

}

if(flag==0 && callStack.empty()) {

System.out.println("Valid Trace");

System.out.println("Maximum call depth was "+callStack.size());

}

if(flag==0 && !callStack.empty())

System.out.println("Not all functions returned");

if(flag==1) {

System.out.println("Stack Trace:");

while(!callStack.empty())

System.out.println(callStack.pop());

}

}

}