PostFix Calculator Project?
Apr 2, 2015
So I am working on a PostFix calculator that is used in command line for a class project, and I am having a little trouble on developing a memory for it. I have been told to create a hashMap and I have researched it and understand the basics of it. I have the calculating method working, but what I am having trouble trying to implement a way for the user to declare variables. For example this what the user should be able to do:
> a = 3 5 + 1 -
7
> bee = a 3 *
21
> a bee +
28
[code]....
I just need to be able to save the answers as a variable the User names, such as the example and let the user be able to use the variables later.
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Nov 16, 2014
My verify method also always returns false. So I'm given three classes to begin with. Calculator, Expression, and InfixExpression and they are listed below.
The goal is to create a class called PostfixExpression that extends Expression and can read and calculate postfix expressions.
My evaluate() method works for most calculations but when it needs to return a negative value it just returns the positive equivalent.
Also, my verify method always returns false and I can't pinpoint why.
Here's my current code. Some things are commented out for debugging purposes.
import java.util.Scanner;
/**
* Simple calculator that reads infix expressions and evaluates them.
*/
public class Calculator
{
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
[Code] .....
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Feb 20, 2014
Our goal is to write a pretty simple program, one that takes the 12 digit UPC code entered by a user and to not only spit it back out in a format with dashes using toString, and also returns the first digit, a 2 more groups of digits numbering 2-6 and 7-11, and finally display the 12th digit. It then performs an equation to check the last digit and make sure the UPC code is correct.
However, being so new to java (I only learned visual basic before), with this I was introduced to two new concepts that for some reason I simply cannot grasp for the life of me: Using and calling the toString method, and calling on methods that are created in a completely different class file.
The first section of code is my UPC class, which is meant to contain all my methods as well as the toString to be called on:
public class UPC
{
// Instance variables
private int itemType; // digit 1
private int manufacturer; // digits 2,3,4,5,6
private int product; // digits 7,8,9,10,11
private int checkDigit; // digit 12
[Code] .....
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Apr 12, 2014
i downloaded a sample database code of an online payroll system. How can i assemble it to know how it works.
the files include php and mysql files. it is to build an online payroll system
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Jun 26, 2014
I tried many times to return a string from java project to an android project But it keeps sending incorrect values as in 2 as it should be 1 here is an example.
Java Project:
boolean somethingboolean = false;
if(something.equals("1")){
somethingboolean = true;
}
public static String getString(){
if(somethingboolean == true){
[Code]...
Android project:
System.out.println(JavaProject.getString())
and in the android project it prints "FALSE"
So what should i do?
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Feb 25, 2014
Case study : infix to postfix conversion, i don't really know how i could make codes, I can understand what is the meaning of infix and postfix but when it comes of making codes i really have a hard time with it.
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Apr 24, 2014
after i am done calculating everything from numbers stack, i pop the last number and return it... my question is how can i catch an exception if the size of my numbers stack is greater than 1;
public static String evaluate(String input) {
char[] a = input.toCharArray();
if (input.isEmpty())
return "No input";
else if (input.equals(" "))
return "No input";
else if (input.equals(" "))
[code]....
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Mar 26, 2015
Will the postfix x++ and the prefix --y change the answer for this question?
If x has the value 10 and so does y, then what is the value of (x ++) * (-- y)?
Answer: 11*9
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Nov 24, 2014
I need to convert infix To Postfix but have a few errors.
Error msg:
PostFix:
Exception in thread "main" java.util.EmptyStackException
at java.util.Stack.peek(Unknown Source)
at java.util.Stack.pop(Unknown Source)
at assignment4.infixToPostfix.evaluatePostfix(infixTo Postfix.java:129)
at assignment4.infixToPostfix.main(infixToPostfix.jav a:19)
NB:
129 >>return (double) s1.pop(); AND 19>>>double ans = evaluatePostfix(postfixStr);
Deadline = less than 1 hour
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Oct 24, 2014
My question is to evaluate a Postfix notation entered from keyboard. I have no errors in my code but it prints only :
Exception in thread "main"
java.util.NoSuchElementException
at ArrayStack.pop(PostFixEvaluation.java:72)
at PostFixEvaluation.evaluatePostfix(PostFixEvaluatio n.java:107)
at PostFixEvaluation.main(PostFixEvaluation.java:140)
I tried many values but it prints the same exception all the time.
Here is my code:
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.NoSuchElementException;
interface Stack<E> {
[Code] ....
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Jul 28, 2014
So my code works perfectly when I input (a+(c-d) and i get ab+cd- for postfix and *+ab-cd for prefix. However when I input a+b+c for infix i receive abc++ postfix and +a+bc prefix when its supposed to be ab+c+ postfix and ++a b c prefix. So my issue is that any infix input with parenthesis, it converts them correctly, however without parenthesis it does not convert correctly.
import java.util.*;
public class stack {
public static char[] convertToPostfix(char[] infixEx) {
Stack<Character> operatorStack = new Stack<Character>();
char[] postfix = new char[infixEx.length];
int index = 0;
[Code] .....
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Apr 13, 2015
package hw9;
import java.util.Scanner;
import java.util.Stack;
public class stack {
public static Integer evaluate(String expression) {
Scanner scanner = new Scanner(expression);
Stack <Integer> operands = new Stack<Integer>();
[Code] ....
When I input my expression which has spaces between characters e.g.:10 2 8 * + 3 -, it worked; when I put expression which may not add space between each char e.g.: 3 14+2*7/, the error showed:
Enter a postfix expression: 3 14+2*7/
Exception in thread "main" java.util.EmptyStackException
at java.util.Stack.peek(Stack.java:102)
at java.util.Stack.pop(Stack.java:84)
at hw9.stack.evaluate(stack.java:22)
at hw9.stack.main(stack.java:45)
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Apr 7, 2014
So I am supposed to be changing infix notation to postfix notation using stacks. This is simply taking a string "3 + 5 * 6" (infix) and turning it into (3 5 6 * +" (postfix).
To do this, we are to scan the string from left to right and when we encounter a number, we just add it to the final string, but when we encounter an operand, we throw it on the stack. Then if the next operand has a higher input precedence than the stack precedence of the operator on the top of the stack, we add that operator to the stack too, otherwise we pop from the stack THEN add the new operator.
I am supposed to be utilizing a hash map but I don't see how you would go about doing this. We are supposed to store operators on the hash map but operators need their own character, input precedence, stack precedence, and rank. How do you use a hash map when you need to tie a character to 3 values instead of just 1? I just don't get it.
The following is our Operator class that we are to use. Another problem is this isn't really supposed to be modified, yet we were given two important variables (inputPrecedence and outputPrecedence) that we can't have nothing to be initialized to and no way of accessing? So that might be where a hash map comes in but I am not sure. I am not very sure on how they exactly work anyway...
public class Operator implements Comparable<Operator>
{
public char operator; // operator
privateint inputPrecedence; // input precedence of operator in the range [0, 5]
privateint stackPrecedence; // stack precedence of operator in the range [-1, 3]
[Code] ....
So my question mostly revolves around how I tie an Operator character to its required values, so I can use it in my code to test two operators precedence values.
My original thought was turn string into character array, but then I would need nested for/while loops to check if it is a number or letter, or if it is an operator and thus result in O(n^2) time
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May 6, 2014
I'm doing a project and my code won't compile.
import javax.swing.*;
import java.awt.event.*;
public class BookStore extends JFrame{
private JPanel panel;
private JLabel question; //This will be where the question is.
private JTextField NumofBooks; //this is where the user will enter the number of books
private JButton OKButton,ClearButton,ExitButton; //Will give the user the points, cancel the points, and exit
private final int WINDOW_WIDTH = 310; //Need to make it visible
private final int WINDOW_HEIGHT = 100;
[code]....
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Nov 24, 2014
I am deploy my project in a machine and access it through VPN. In one page i am sending parameters array through hidden input field. When i access it in process page through request.getParameterValues it return null values, you can see it in attachment.This page work fine without VPN.
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Feb 10, 2015
i have programmed a game using JPanel and JFrame. My App is of this type (if this is relevant to the problem):
public class Main extends JPanel {
private JFrame frame;
public static void main(String[] args) {
new Main();
} public Main() {
frame.setSize(WIDTH, HEIGHT);
[Code] ....
The problem is, When i export the file in eclipse as Runnable jar file,and run the exported file, it gives me a blank screen (white default) and nothing is running. Whereas, normal debugging of the game is working quite well.
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Mar 5, 2015
So, I've been working on a school project for a couple days, and I have my code written out but I can't fix the compile-time errors. The prompt for it is here:
Write two programs: one using the String class and one using the StringBuffer class. Your programs should store a set of Strings in an ArrayList and print those Strings in the order by which they are added. The output of your programs should create a complete sentence.
I am stuck on the first program.Here's my code for the first program:
Java Code:
import java.util.ArrayList;
public class SentenceNormal {
public static void main(String args[]) {
String n1 = "My ";
String n2 = "favorite ";
String n3 = "football ";
String n4 = "team ";
String n5 = "is ";
String n6 = "the ";
String n7 = "Seahawks";
[code]....
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May 27, 2014
As a brand new with Java I've created a small "Hello world" program using eclipse.
I would like to create an exe file from this application. Therefore, I need the jar file.
I can't find such a file with that extension in the folder where I saved the java project.
How can I manage this file?
I know it is a very basic issue, but as I mentioned it is the first "Hello world" test...
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Sep 23, 2014
Hello World program. We had to build it. Write a basic Java program that will implement one class to store a state of a project. The class should have one property to store a textual name of the state. When a object of this class is created the initial state should be "Open".
1) Class should have one method next() which will move the project to the next step in the sequence: Open - In progress - Closed.If next method is called for a project in the Closed state it should do nothing.
2) Class should have a method close() which will move the project into the Closed state.
3) Class should have a method print() that will output a current state of the project.
Submit a java code file as your assignment. Do not hesitate to contact me if you have any troubles with the assignment.
I have been working on this thing for almost a week, and really don't have a clue on what to do. I know I have to use a string = open, and I know I have to create an object. I don't have a clue on how to do this. I have read the chapter so many times, I almost memorized it, but what he wants is nothing like our demo in the book. the Book used set and get, and utility scanner, but he doesn't want any of that. Just a basic code that will move from Open --- in progress --- closed.
The best I can tell what he wants is when I set the object to open it will display " project is open", then when I set it to " in progress" it will read project is "in progress". I don't have a clue what close is suppose to do, or the print method.
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Dec 7, 2014
I have make a simple grade average project and can't figure out how to ask the user if they want to enter more grades to average and run the app again.Here's what I have so far.
import java.util.Scanner;
public class Average {
private static Scanner kb;
public static void main(String[] args) {
kb = new Scanner(System.in);
[code]...
How many grades do you wish to average?
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May 12, 2014
I'm done with my project and I'm not trying to make it into a jar with JGrasp... I start by making a project then I click the option to make my project into a jar... Everything works but when I try to run it it says that the main class cannot be found... How can I fix this?
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Jul 8, 2014
i don't know how create that project ,
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Apr 20, 2014
I inherited a web application and am trying to build it. I recently installed JasperSoft Studio 5.5.0 final on my developer machine. I also have Eclipse Juno on my developer machine. I was advised by the previous developer to put some of his Jasper .jar files into my web app's lib folder. I did do this and now the localhost will not run, it is generating this error:
org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:502)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:430)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
I went out to the lib folder and saw these files:
jasperreports-5.1.2
jasperreports-applet-5.1.2
jasperreports-expressions-1.0.0
jasperreports-exprfunction-1.0.0
jasperreports-fonts-5.1.2
jasperreports-javaflow-5.1.2
The version on them would appear incorrect given my version of 5.5. I am new to Jasper Reports. I suppose I could google on the .jar files and get the ones that belong to the 5.5.0 final and put them into the directory to see if Apache Tomcat 6.0.39 likes that better. And then start the server. If it doesn't like them, I guess I could remove them and continue, but I would prefer to have the Jasper Reports up and running.
My second question about the Jasper Reports is how do you tell the IDE where the Reports are located?
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May 26, 2014
I bought a certificate to sign my jars, if a deploy my applet in a html file with out framework, just html and js, the works great, I can call from javascript all public methods from the applet. The real problem is when I try to deploy the same signed jar on a adf project in Jdeveloper. Does not work at all and java execute some warnings and later applet is block, the message say something like "exist some jars signed and not signed" But I am sure that all jars are signed...
I got this:
applet console:
image
All jars are signed, dependencies too.
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Nov 20, 2014
I use a program called eclipse. I want to know how to build a house with the program. We use a pen in java. It is a drawing tool. I dont know how to do it.
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Feb 21, 2014
So I have 3 classes in this project, and When it compiles, I get a null pointer.
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;
public class Project2 {
[Code] .....
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