Develop Reference

Can't figure out why my counter is broken?

I am a somewhat intermediate-level Java programmer but I have had trouble with one of my recent programs. Basically the application is a Hangman game that allows the user to input letters in order to guess a word. Everything works okay except for the counter for how many lives the player has, in this case it is 5. The counter for some reason subtracts by 4 instead of 1, as well as this it takes away from the number of lives even if the letter is guessed correctly.
Any help would be widely appreciated, thank you in advance. The two classes are provided below. Also,
Instantiable Class
public class Hangman {
private char letterGuess;
private int numberLives;
private String outputWord;
private final String hiddenWord;
private final StringBuffer swapBuffer = new StringBuffer();
public Hangman() {
letterGuess = ' ';
numberLives = 5;
hiddenWord = "java";
outputWord = "";
for (int i = 0; i < hiddenWord.length(); i++) {
swapBuffer.append("*");
}
}
public void setLetterGuess(char letterGuess) {
this.letterGuess = letterGuess;
}
public void compute() {
for (int i = 0; i < hiddenWord.length(); i++) {
if (letterGuess == hiddenWord.charAt(i)) {
swapBuffer.setCharAt(i, letterGuess);
}
else {
numberLives--;
}
}
outputWord = swapBuffer.toString();
}
public int getNumberLives() {
return numberLives;
}
public String getHiddenWord() {
return hiddenWord;
}
public String getOutputWord() {
return outputWord;
}
}
Main Class
import javax.swing.*;
public class HangmanApp {
public static void main(String[] args) {
char letterGuess;
int numberLives;
String hiddenWord, outputWord, restartGame;
do {
Hangman myHangman = new Hangman();
JOptionPane.showMessageDialog(null, "Welcome to Java Hangman!");
JOptionPane.showMessageDialog(null, "In this game, a word will be printed to you in asterisks - each letter will be revealed upon a correct guess!");
JOptionPane.showMessageDialog(null, "You have 5 lives for the game, the game will end if you make too many incorrect guesses!");
for (int i = 0; i < 10; i++) {
hiddenWord = myHangman.getHiddenWord();
numberLives = myHangman.getNumberLives();
JOptionPane.showMessageDialog(null, "You currently have " +numberLives+ " lives!");
letterGuess = JOptionPane.showInputDialog(null, "Now, please enter a letter : ").charAt(0);
myHangman.setLetterGuess(letterGuess);
myHangman.compute();
outputWord = myHangman.getOutputWord();
JOptionPane.showMessageDialog(null, "The word so far is : " +outputWord);
}
numberLives = myHangman.getNumberLives();
JOptionPane.showMessageDialog(null, "You have finished the game with : " +numberLives+ " lives!");
restartGame = JOptionPane.showInputDialog(null, "Would you like to play again?");
}
while (restartGame.equalsIgnoreCase("Yes"));
}
}

Use a found boolean to check if the letter was found. If it wasn't, subtract a life.
var found = false;
for (int i = 0; i < hiddenWord.length(); i++) {
if (letterGuess == hiddenWord.charAt(i)) {
swapBuffer.setCharAt(i, letterGuess);
found = true;
}
}
if (!found) numberLives--;

If the guessed letter is wrong, in the compute function 1 life will be taken for each letter of the hidden word. You should try and use a switch(boolean) that will show you if the letter was found or not after parsing the whole word.
public void compute() {
// for (int i = 0; i < hiddenWord.length(); i++) {
// if (letterGuess == hiddenWord.charAt(i)) {
// swapBuffer.setCharAt(i, letterGuess);
// }
//
// else {
// numberLives--;
// }
// }
int letterNo = hiddenWord.length();
boolean found = false;
while (letterNo>0){
letterNo--;
if (letterGuess == hiddenWord.charAt(letterNo)){
swapBuffer.setCharAt(letterNo, letterGuess);
found = true;
}
}
if (!found){
numberLives--;
}
outputWord = swapBuffer.toString();
}

Dice roller Java returns less random results

i'm trying to make a little program thar throws "reservaDados" number of dice and compare the "dado" (who is a number between 1-10) to a specified dificulty. Then i want to print the count of the number of exits, fails and ultrafails, but i seem to have a problem with the number of times the loop works, it only prints 9 results and i don't seem to find why, i supose that it has to do something with the counter i?
import java.util.*;
public class ProgramTUI {
public static void main(String[] args) {
Scanner var = new Scanner(System.in).useLocale(Locale.ENGLISH);
System.out.print("Cuantos dados lanzas?");
int reservaDados = var.nextInt();
System.out.print("Cual es la dificultad?");
int dificultad = var.nextInt();
int i = 0;
int numero_exitos = 0;
int numero_fracasos = 0;
int numero_pifias = 0;
while (i < reservaDados) {
i++;
int dado = (int) (Math.random() * 10) + 1;
if (reservaDados == i) {
System.out.println("Has sacado " + numero_exitos + " exitos, " + numero_fracasos
+ " fracasos, " + numero_pifias + " pifias");
} else if (dado == 1) {
numero_pifias++;
} else if (dado < dificultad) {
numero_fracasos++;
} else {
numero_exitos++;
}
}
}
}

In the last iteration, no more counting is done, only the result is printed. So you effectively miss one iteration.
Could be fixed by removing the first else, or by doing one extra iteration.
But just take the whole result printing out of the loop and place it directly after the loop. That will make the intent of the code much clearer.

Thilo is right, in the last pass of the loop it dosn't count the dice because ther is a print first, i just taked out the print, and pasted at the end like this:
import java.util.*;
public class ProgramTUI {
public static void main(String[] args) {
Scanner var = new Scanner(System.in).useLocale(Locale.ENGLISH);
System.out.print("Cuantos dados lanzas?");
int reservaDados= var.nextInt();
System.out.print("Cual es la dificultad?");
int dificultad= var.nextInt();
int i=0;
int numero_exitos=0;
int numero_fracasos=0;
int numero_pifias=0;
while (i < reservaDados){
i++;
int dado= (int) (Math.random() * 10) + 1;
if (dado == 1) {numero_pifias++;}
else if (dado < dificultad) {numero_fracasos++;}
else {numero_exitos++;}
if (reservaDados == i){System.out.println("Has sacado "+numero_exitos+" exitos, "+numero_fracasos+" fracasos, "+numero_pifias+" pifias");}
}
}
}
And it was fixed, thanks!

From String to Integer Functions

I am trying to write a program that will receive a function as a String and solve it. For ex. "5*5+2/2-8+5*5-2" should return 41
I wrote the code for multiplication and divisions and it works perfectly:
public class Solver
{
public static void operationS(String m)
{
ArrayList<String> z = new ArrayList<String>();
char e= ' ';
String x= " ";
for (int i =0; i<m.length();i++)
{
e= m.charAt(i);
x= Character.toString(e);
z.add(x);
}
for (int i =0; i<z.size();i++)
{
System.out.print(z.get(i));
}
other(z);
}
public static void other(ArrayList<String> j)
{
int n1=0;
int n2=0;
int f=0;
String n= " ";
for (int m=0; m<j.size();m++)
{
if ((j.get(m)).equals("*"))
{
n1 = Integer.parseInt(j.get(m-1));
n2 = Integer.parseInt(j.get(m+1));
f= n1*n2;
n = Integer.toString(f);
j.set(m,n);
j.remove(m+1);
j.remove(m-1);
m=0;
}
for (int e=0; e<j.size();e++)
{
if ((j.get(e)).equals("/"))
{
n1 = Integer.parseInt(j.get(e-1));
n2 = Integer.parseInt(j.get(e+1));
f= n1/n2;
n = Integer.toString(f);
j.set(e,n);
j.remove(e+1);
j.remove(e-1);
e=0;
}
}
}
System.out.println();
for (int i1 =0; i1<j.size();i1++)
{
System.out.print(j.get(i1)+",");
}
However, for adding and subtracting, since there isnt an order for adding and subtracting, just whichever comes first, I wrote the following:
int x1=0;
int x2=0;
int x3=0;
String z = " ";
for (int g=0; g<j.size();g++)
{
if ((j.get(g)).equals("+"))
{
x1= Integer.parseInt(j.get(g-1));
x2= Integer.parseInt(j.get(g+1));
x3= x1+x2;
z = Integer.toString(x3);
j.set(g,z);
j.remove(g+1);
j.remove(g-1);
g=0;
}
g=0;
if ((j.get(g)).equals("-"))
{
x1= Integer.parseInt(j.get(g-1));
x2= Integer.parseInt(j.get(g+1));
x3= x1-x2;
z = Integer.toString(x3);
j.set(g,z);
j.remove(g+1);
j.remove(g-1);
g=0;
}
g=0;
}
System.out.println();
for (int i1 =0; i1<j.size();i1++)
{
System.out.print(j.get(i1)+",");
}
After this, it prints:
25,+,1,-,8,+,25,–,2,
. What am I doing wrong? Multiplication and dividing seem to be working perfectly

You have 2 problems:
1) g=0; statements after if and else blocks will make you go into an infinite loop.
2) From the output you gave, the first minus (-) is Unicode character HYPHEN-MINUS (U+002D), while the second minus (–) is Unicode character EN DASH (U+2013), so (j.get(g)).equals("-") fails for the second minus as they are not equal.

Going for an answer that doesn't help with your exact specific problem, but that hopefully helps you much further than that.
On a first glance, there are various problems with your code:
Your are using super-short variable names all over the place. That saves you maybe 1 minute of typing overall; and costs you 5, 10, x minutes every time you read your code; or show it to other people. So: dont do that. Use names that say what the thing behind that name is about.
You are using a lot of low-level code. You use a "couting-for" loop to iterate a list (called j, that is really really horrible!) for example. Meaning: you make your code much more complicated to read than it ought to be.
In that way, it looks like nobody told you so far, but the idea of code is: it should be easy to read and understand. Probably you dont get grades for that, but believe me: in the long run, learning to write readable code is a super-important skill. If that got you curious, see if you can get a hand on "Clean code" by Robert Martin. And study that book. Then study it again. And again.
But the real problem is your approach to solve this problem. As I assume: this is some part of study assignment. And the next step will be that you don't have simple expressions such as "1+2*3"; but that you are asked to deal with something like "sqrt(2) + 3" and so on. Then you will be asked to add variables, etc. And then your whole approach breaks apart. Because your simple string operations won't do it any more.
In that sense: you should look into this question, and carefully study the 2nd answer by Boann to understand how to create a parser that dissects your input string into expressions that are then evaluated. Your code does both things "together"; thus making it super-hard to enhance the provided functionality.

You can use the built-in Javascript engine
public static void main(String[] args) throws Exception{
ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine engine = mgr.getEngineByName("JavaScript");
String code = "5*5+2/2-8+5*5-2";
System.out.println(engine.eval(code));
}

Primarily Don't Repeat Yourself (the DRY principle). And use abstractions (full names, extracting methods when sensible). Static methods are a bit cumbersome, when using several methods. Here it is handy to use separate methods.
Maybe you want something like:
Solver solver = new Solver();
List<String> expr = solver.expression("5*5+2/2-8+5*5-2");
String result = solver.solve(expr);
A more abstract Solver class would do:
class Solver {
List<String> expression(String expr) {
String[] args = expr.split("\\b");
List<String> result = new ArrayList<>();
Collections.addAll(result, args);
return result;
}
String solve(List<String> args) {
solveBinaryOps(args, "[*/]");
solveBinaryOps(args, "[-+]");
return args.stream().collect(Collectors.joining(""));
}
The above solveBinaryOps receives a regular expression pattern or alternatively simply in some form the operators you want to tackle.
It takes care of operator precedence.
private void solveBinaryOps(List<String> args, String opPattern) {
for (int i = 1; i + 1 < args.length; ++i) {
if (args.get(i).matches(opPattern)) {
String value = evalBinaryOp(args.get(i - 1), args.get(i), args.get(i + 1));
args.set(i, value);
args.remove(i + 1);
args.remove(i - 1);
--i; // Continue from here.
}
}
}
private String evalBinaryOp(String lhs, String op, String rhs) {
int x = Integer.parseInt(lhs);
int y = Integer.parseInt(rhs);
int z = 0;
switch (op) {
case "*":
z = x * y;
break;
case "/":
z = x / y;
break;
case "+":
z = x + y;
break;
case "-":
z = x - y;
break;
}
return Integer.toString(z);
}
}
The above can be improved at several points. But it is readable, and rewritable.

public class Solver {
public static void main(String args[]) {
operation("5+2*5-6/2+1+5*12/3");
}
public static void operation(String m) {
ArrayList<Object> expressions = new ArrayList<Object>();
String e;
String x = "";
for (int i = 0; i < m.length(); i++) {
e = m.substring(i, i + 1);
if (!(e.equals("*") || e.equals("/") || e.equals("+") || e
.equals("-"))) {
x += e;
continue;
} else {
if (!x.equals("") && x.matches("[0-9]+")) {
int oper = Integer.parseInt(x);
expressions.add(oper);
expressions.add(m.charAt(i));
x = "";
}
}
}
if (!x.equals("") && x.matches("[0-9]+")) {
int oper = Integer.parseInt(x);
expressions.add(oper);
x = "";
}
for (int i = 0; i < expressions.size(); i++) {
System.out.println(expressions.get(i));
}
evaluateExpression(expressions);
}
public static void evaluateExpression(ArrayList<Object> exp) {
//Considering priorities we calculate * and / first and put them in a list mulDivList
ArrayList<Object> mulDivList=new ArrayList<Object>();
for (int i = 0; i < exp.size(); i++) {
if (exp.get(i) instanceof Character) {
if ((exp.get(i)).equals('*')) {
int tempRes = (int) exp.get(i - 1) * (int) exp.get(i + 1);
exp.set(i - 1, null);
exp.set(i, null);
exp.set(i + 1, tempRes);
}
else if ((exp.get(i)).equals('/')) {
int tempRes = (int) exp.get(i - 1) / (int) exp.get(i + 1);
exp.set(i - 1, null);
exp.set(i, null);
exp.set(i + 1, tempRes);
}
}
}
//Create new list with only + and - operations
for(int i=0;i<exp.size();i++)
{
if(exp.get(i)!=null)
mulDivList.add(exp.get(i));
}
//Calculate + and - .
for(int i=0;i<mulDivList.size();i++)
{
if ((mulDivList.get(i)).equals('+')) {
int tempRes = (int) mulDivList.get(i - 1) + (int) mulDivList.get(i + 1);
mulDivList.set(i - 1, null);
mulDivList.set(i, null);
mulDivList.set(i + 1, tempRes);
}
else if ((mulDivList.get(i)).equals('-')) {
int tempRes = (int) mulDivList.get(i - 1) - (int) mulDivList.get(i + 1);
mulDivList.set(i - 1, null);
mulDivList.set(i, null);
mulDivList.set(i + 1, tempRes);
}
}
System.out.println("Result is : " + mulDivList.get(mulDivList.size() - 1));
}
}

Program freezes when trying to analyse a string

I am writing on a method which should analyse a polynomial given by the user (as String) and do different stuff with it in the future. At the moment, I was trying to test the code I have so far but whenever I execute the program, it freezes and after sitting for hours in front of the computer I still can't find the culprit in it.
I was testing if a polynomial of one variable could be analysed and then re-printed, but it doesn't work.
I hoped anyone could help me out on this.
Here's the code block in the main which executes the method, the string userInput is a polynomial (e.g 4x-6x^2):
String userInput = inputArea.getText().trim();
Monomials monomials = new Monomials();
monomials.analyse(userInput);
Here's the class monomials with its method analyse():
//Class Monomial
class Monomials
{
private int coeff = 0;
private char var;
private int addpow = 1;
private int pow;
private char powsign = '^';
private char minus = '-';
private boolean isnegative = false;
private String mono;
StringBuilder stringBuilder = new StringBuilder();
public int getCoeff(int coeff)
{
return coeff;
}
public void setCoeff(int coeff)
{
this.coeff = coeff;
}
public void setVar(char var)
{
this.var = var;
}
public void setPow(int pow)
{
this.pow = pow;
}
public String getMono(String monomials)
{
return mono;
}
// Method to further analyse user's input.
public void analyse(String polynomial)
{
//Split the poynomial into monomials and store them in an array list.
polynomial = polynomial.replaceAll("-","+-");
String polyParts[] = polynomial.split("\\+");
ArrayList<String> monomials = new ArrayList<String>(Arrays.asList(polyParts));
// Iterate the monomials.
for (int i = 0; i <= monomials.size(); i++)
{
String monomial = monomials.get(i);
// Analyse the monomial.
for (int x = 0; x <= monomial.length(); x++)
{
char c = monomial.charAt(x);
int countcoeff = 0;
int countvar = 0;
// check if negative.
if (c == minus)
{
isnegative = true;
x++;
}
// get the coefficient.
if (Character.isDigit(c))
{
while (Character.isDigit(c))
{
countcoeff++;
x++;
}
if (isnegative)
{
setCoeff(Integer.parseInt(monomial.substring(1, countcoeff)));
} else
{
setCoeff(Integer.parseInt(monomial.substring(0, countcoeff)));
}
}
// get the variable.
if (Character.isLetter(c))
{
char var = c;
while (Character.isLetter(var))
{
countvar++;
addpow++;
x++;
}
}
// get the power.
if (c == powsign)
{
countvar++;
x++;
while (Character.isDigit(c))
{
x++;
}
if (isnegative)
{
setPow(Integer.parseInt(monomial.substring(countcoeff+countvar+2, x)));
} else
{
setPow(Integer.parseInt(monomial.substring(countcoeff+countvar+1, x)));
}
pow += addpow;
}
}
if (isnegative)
{
stringBuilder.append(String.valueOf(minus));
}
stringBuilder.append(String.valueOf(coeff) + String.valueOf(var) + String.valueOf(powsign) + String.valueOf(pow));
mono = stringBuilder.toString();
monomials.set(i, mono);
}
for (int i = 0; i < monomials.size(); i++)
{
System.out.println(String.valueOf(monomials.get(i)));
}
} // End of method analyse().
} // End of class Monomial

You have a couple of loops which will never exit:
while (Character.isDigit(c))
{
countcoeff++;
x++;
}
How to find out Stuff like that?
If you use Eclipse, you can run your Code in Debug Mode, switch to the debug-perspective and click on the yellow Suspend-Symbol. That will suspend your Program, in the Debug-View you can see in which line the Thread is "hanging", if you click on it it will open the source-code.
If you don't use an IDE with that function, you can use the JDK-Tools: Use jps to find out the ID of your program:
C:\jdk\jdk8u45x64\jdk1.8.0_45\bin>jps
7216
5688 Jps
6248 Monomials
Then use jstack to print a stack trace of all running threads:
C:\jdk\jdk8u45x64\jdk1.8.0_45\bin>jstack 6248
[other threads omitted]
"main" #1 prio=5 os_prio=0 tid=0x000000000203e800 nid=0x1b2c runnable [0x000000000201e000]
java.lang.Thread.State: RUNNABLE
at Monomials.analyse(Monomials.java:77)
at Monomials.main(Monomials.java:10)

one of your loop is running infinitely. You should replace it with if condition.
while (Character.isDigit(c))
{
countcoeff++;
x++;
}
replace it with
if (Character.isDigit(c))
{
countcoeff++;
x++;
}
Or you could use break statement here.

As the others stated already
while (Character.isDigit(c))
is your problem.
But you have that two times not one time, so both are a problem. The 2nd isn't a real problem, because Character.isDigit and if (c == powsign) can´t be both true at the same time, so the 2nd inifit loop never gets executed, which brings me to the next point: bugs.
In your code there are a tremendous amount of them :-D
Both for loops are running to far (<= .size() & <= .length()), replace <= with <.
Also, the x++ placed around in your code are wrong. x gets incremented automaticially and if you want to exit the loop early, use break; or use continue; if you want to jump to the next iteration early.

Issue with Threading

I want to be able to use threads to run two loops at once within my program for a sort of game like program. However I'm not entirely sure how to use Threads and I am encountering errors I know nothing about. I will post code but ignore most of it, it's a somewhat hollow shell of what I want it to be I just need to get threads working to start cleaning it all up.
I'm getting the error "is not abstract and does not override" and it is highlighting the "class game implements runnable" section. This is the code:
public class game implements Runnable
{
#Override
public void run(int time){
try{
time = 1;
while (time<=10){
Thread.sleep(10);
System.out.print(time);
time++;
}
char clearer = (char)(12);
System.out.print(clearer);
System.out.println("You have ran out of time! Game over!");
System.exit(0);
}catch (Exception e){}
}
public static void main (String args[]) throws Exception{
System.out.println("Welcome to pseudo-Where's Wally, look for the lower cal l character.");
Thread.sleep(500);
System.out.println("You get 10 seconds to find it.");
Thread.sleep(500);
System.out.println("Ready?..");
char clear = (char)(12);
Thread.sleep(500);
System.out.print(clear);
boolean timer = false, col = false, guess = false;
int length = 5, time = 0, rowNum = 1, y = 0;
String manip = ("");
int x = (length*length);
Random gen = new Random();
int find = gen.nextInt(x)+1;
for (int collumn = 0; collumn<=length; collumn++){
for (int row = 0; row<=length; row++){
while (!col){
y++;
System.out.print(" "+y);
if (y-1 == length){
System.out.println();
System.out.println();
col = true;
}
}
System.out.print(" I");
manip = manip + (" I");
}
System.out.println("\t" + rowNum);
rowNum++;
manip = manip + (" I");
}
boolean contin = false;
do{
if (find%3==0){
contin = true;
find = find - 1;
} else if (find%3>0){
find = find - 1;
}
}while (!contin);
String newManip = manip.substring(0,find)+'l'+manip.substring(find+1);
String subOne = newManip.substring(0,18);
String subTwo = newManip.substring(18,36);
String subThree = newManip.substring(36,54);
String subFour = newManip.substring(54,72);
String subFive = newManip.substring(72,90);
String subSix = newManip.substring(90,108);
System.out.println(subOne);
System.out.println(subTwo);
System.out.println(subThree);
System.out.println(subFour);
System.out.println(subFive);
System.out.println(subSix);
Thread threadA = new ThreadA();
threadA.start();
while(guess != true){
System.out.print("Answer (Only one try): ");
int answer = sc.nextInt();
if (answer == finalAnswer){
guess = true;
}
}
}
}
Cheers for any help.

In order to implement Runnable you need to override the run() method (unless your class is abstract, which opens another discussion). What you have in your game class is run(int time), which won't count.
From the Runnable API:
The Runnable interface should be implemented by any class whose instances are intended to be executed by a thread. The class must define a method of no arguments called run.
Bold added by me.