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Thread: LinkedStack - need help fixing code; should be quick fix

  1. #1
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    Default LinkedStack - need help fixing code; should be quick fix

    I included my Driver class, prompt, input, and output: my pop/peek commands aren't working properly - please help!

    DRIVER:
    //Lab 9
    //Ashmi Patel
    /* Implement and test a LinkedStack.
    Activities:
    1. Complete the implementation of the LinkedStack example provided in your text and in class. Preserve the
    packaging of the source code in the javafoundations and javafoundations.exceptions packages.
    That is, the Stack, LinkedStack and LinearNode classes should be located in the javafoundations
    package, and the required exception classes should be located in the javafoundations.exceptions
    package.
    2. Create a Driver class that exercises (tests) the functionality of the LinkedStack you implemented. That is,
    create a LinkedStack<String> object in the Driver. Once created, open and read from an input file named
    “lab9.inp” which contains an unknown number of “commands”, one per line. For testing your lab, you can create
    your own input file, as per the command specifications below, but the input file I use to grade your lab will be of
    my creation (and not released to you).
    3. The input file will contain an unknown number of lines, each with a command on it that mimics a stack
    operation. The details of the format, parameter (if any) and purpose of each command (as well as a small sample
    input file) are shown below. When the program runs and reads from the input file, each command will be
    processed in turn usually performing one or more operations on the stack of strings you have created in this lab.
    Handle gracefully (catch and continue processing the next line) any exceptions (including input, or stack-based).
    */
     
    import javafoundations.*;
    import javafoundations.exceptions.EmptyCollectionException;
    import java.io.*;
    import java.util.Scanner;
     
    public class Driver{
     
    	public static void main(String[] values){
     
    		LinkedStack<String> stack = new LinkedStack<String>();
     
    		File input;
    		Scanner scanner;
    		Scanner parser;
    		String command;
    		String value;
     
    		try {
    			input = new File("lab9.inp");
    			scanner = new Scanner(input); }
    		catch(FileNotFoundException e){
    			System.err.println("Input file 'lab9.inp' does not exist.");
    			return; }
    		while(scanner.hasNextLine()){
    			parser=new Scanner(scanner.nextLine());
    			command=parser.next();
    			if(parser.hasNext()){
    				value=parser.next(); }
    			else{
    				value=""; }
    			//push
    			if(command.compareTo("push")==0){
    				stack.push(value); }
    			//pop
    			try{
    				if(command.compareTo("pop")==0){
    					System.out.println(stack.pop()); } }
    			catch(EmptyCollectionException e){
    				System.err.println("Nothing to pop"); }
    			//peek
    			try{
    				if(command.compareTo("peek")==0){
    					System.out.println(stack.peek()); }} 
    			catch(EmptyCollectionException e){
    				System.err.println("Nothing to peek"); }
    			//size
    			if(command.compareTo("size")==0){
    				System.out.println("The size of the stack is currently " + stack.size()); }
    			//isEmpty
    			if(command.compareTo("isEmpty")==0){
    				if(stack.isEmpty()==true){
    					System.out.println("The stack is empty");}
    				if(stack.isEmpty()==false){
    					System.out.println("The stack is not empty");}}
    			//toString
    			if(command.compareTo("toString")==0){
    				System.out.println(stack.toString());}	
    		}
    	}
    }

    INPUT:
    size
    isEmpty
    push “Dr. Mike Martinovic”
    push “Dr. Andrea Salgian”
    push “Dr. Pete DePasquale”
    push “Dr. Deborah Knox”
    pop
    size
    isEmpty
    pop
    size
    toString
    push “Dr. Jikai Li”
    push “Dr. Monihsa Pulimood”
    peek

    OUTPUT:
    The size of the stack is currently 0
    The stack is empty
    Dr.
    The size of the stack is currently 3
    The stack is not empty
    Dr.
    The size of the stack is currently 2
    <top of stack>
    Dr.
    Dr.
    <bottom of stack>
    Dr.


  2. #2
    Super Moderator Norm's Avatar
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    SW Missouri
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    Default Re: LinkedStack - need help fixing code; should be quick fix

    Please explain what "aren't working properly" means.
    Is there somethings wrong with the output that you posted? Can you explain what the output should be?

    How do you test the code? What you posted has many compiler errors because of missing classes.
    Last edited by Norm; August 28th, 2012 at 07:14 AM.
    If you don't understand my answer, don't ignore it, ask a question.

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