Develop Reference

Trying to print a method using another method

Not sure where I'm going wrong with this. I've asked someone in my class and they said there should be an argument with "toonRijSterren". when I do this I just get more errors, could someone have a look and tell me where I'm going wrong?
public static void main(String[] args) {
int aantal = 0;
toonRijSterren(aantal);
toonSterrenVierkant(aantal);
}
public static void toonRijSterren(int mpAantal) {
while (mpAantal < 6) {
System.out.print(" * ");
mpAantal++;
}
}
public static void toonSterrenVierkant(int mpAantal) {
for (int mpAatal = 0; mpAantal < 6; mpAantal++) {
System.out.println(toonRijSterren());
}
}
ther error line is in the brackets of the last toonRijSterren());

toonRijSterren is void method which means it does not return any value and therefore you can not put it inside System.out.println() or you can not assign it to some variable.
toonRijSterren expects an int argument which you have missed while calling it.
Given below is an example of how you should call toonRijSterren:
public static void toonSterrenVierkant(int mpAantal) {
for (int mpAatal = 0; mpAatal < 6; mpAatal++) {
toonRijSterren(mpAantal);
}
}

You are not passing the argument when you call your method.
Try this:
System.out.println(toonRijSterren(mpAatal));

First of all, your function toonRijSterren takes an int type parameter (according to its declaration), so you need to pass to it another argument. For example:
toonRijSterren(mpAantal)
Second, the function toonRijSterren returns void. That means, it just does an operation (in this case, printing) without returning anything. What you're trying to do is to use its return value (which doesn't exist) as an argument to System.out.println, which causes an error (because println expects an argument of some type).
You could achieve what I think you're trying to do with the line:
toonRijSterren(mpAantal);.
The function itself prints the values, so the println here is unnecessary and causes an error.

You are missing the parameter in your toonSterrenVierkant() function where you calling toonRijSterren.
Here is the corrected version of your code:
public static void toonSterrenVierkant(int mpAantal) {
for (; mpAantal < 6; mpAantal++) {
toonRijSterren(mpAatal);
}
}

As your methed toonSterrenVierkant(int mpAantal) has a int parameter, you must pass an int value as an argument in the last toonRijSterren(). For example, replace the line System.out.println(toonRijSterren()); with System.out.println(toonRijSterren(1));

Returning the length of my group to my int

package files;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Regex {
public static String arr[];
public static void main(String[] args) throws Exception {
String fiveFour="kkkkaaaaa";
String condition="[a]{5}|[k]{1}";
int size=0;
regTest(condition,fiveFour,size);
System.out.println(size);
}
public static int regTest(String regexThing, String toCheck, int size){
Pattern pattern= Pattern.compile(regexThing);
Matcher regexMatcher= pattern.matcher(toCheck);
int i=0;
while(regexMatcher.find()){
i++;
System.out.println(regexMatcher.group());
if(regexMatcher.group().length()!=0){
System.out.println(regexMatcher.group().length());
}
}
return i;
}
// work on return try maybe a increment and returning that at the end!
//stacks
}
I'm having trouble returning my regexMatcher.group().length(), in my sop it prints out 5 which is correct. However it won't assign that value to size so I can return it. Any help? It's a logic error and I don't see where I went wrong.
package files;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Regex {
public static String arr[];
public static void main(String[] args) throws Exception {
String fiveFour="kkkkaaaaa";
String condition="[a]{5}|[k]{1}";
int size=0;
regTest(condition,fiveFour,size);
System.out.println(size);
}
public static int regTest(String regexThing, String toCheck, int size){
Pattern pattern= Pattern.compile(regexThing);
Matcher regexMatcher= pattern.matcher(toCheck);
int i=0;
while(regexMatcher.find()){
i++;
System.out.println(regexMatcher.group());
if(regexMatcher.group().length()!=0){
System.out.println(regexMatcher.group().length());
i++;
}
}
return size;
}
// work on return try maybe a increment and returning that at the end!
//stacks
}

You're never assigning the result of regexMatcher.group().length() to size.
So there are two things you need to change, the first is that inside your method, you want to add:
size = regexMatcher.group().length();
Now, inside the regTest method size has the value of 5 that you're expecting. BUT, because Java passes primitives by value (see this question for more explanation of what that means), this means that the size you pass in to the method is different from the size in the main method, so you have more to do.
You return the size from your method, so in the caller, you can assign that to the original size variable, like:
size = regTest(condition, fiveFour, size);
Now, because you're never actually using the size parameter in the regTest method, you don't actually need to pass it in, because you only actually care about it as the return value, so it might be cleaner to just have, in your main method:
int size = regTest(condition, fiveFour);
And then in the regTest method, get rid of size altogether and just have:
return regexMatcher.group().length();

The pattern ensures that the groups matching to the criteria are returned. No need to extra validation if(regexMatcher.group().length()!=0).
primitive data types in java are immutable.
If your intention is to find the total groups then the value i would give the same.
Refer http://www.vogella.com/tutorials/JavaRegularExpressions/article.html

How to create boolean array in global - Java

I want create Boolean array in global, here code i tried to make
public class BettingHandler extends BaseClientRequestHandler
{
public static int player[] = new int [100];
public static int i;
public static boolean playerAct[];
public void handleClientRequest(User user, ISFSObject params)
{
RouletteExtension gameExt = (RouletteExtension) getParentExtension();
if (BettingHandler.player[BettingHandler.i] != -1)
{
trace("player problem");
BettingHandler.player[BettingHandler.i] = user.getPlayerId();
BettingHandler.playerAct[BettingHandler.i] = true;
i++;
}
trace("If this showed, no error");
}
}
In Eclipse not showed redcross sign in left this code
public static boolean playerAct[];
and here
BettingHandler.playerAct[BettingHandler.i] = true;
I make this for handler in SFS2X, so i check error in SFS2X zone monitor but unfortunately, this script just run till this
trace("player problem");
when remove this code
BettingHandler.playerAct[BettingHandler.i] = true;
script run till this
trace("If this showed, no error");
so i know something wrong with BettingHandler.playerAct[BettingHandler.i] = true;, How could I fix my code?

You never initialized the array but you are trying to use it.
public static boolean playerAct[] = new boolean[100];

Funny thing:
public static int player[] = new int [100];
public static int i;
public static boolean playerAct[];
The first array, there you actually create an array for 100 elements.
You omit that step for your second array. And you are really surprised that the second gives you problems?
Besides: whatever framework your are working with; maybe you should first step back and learn some more about the basics of Java. For example, the above code might work when fixed; but doing everything with public static variables ... looks very much like bad design.

I want to check the number of characters in a String method

I want to check that a certain number of characters in a method that inputs and returns string
public static String watsonCrick(String dna){
dna = "ATA";
int length = dna.length();
char firstCharacter = dna.charAt(0);
char secondCharacter = dnaSequence.charAt(1);
char thirdCharacer = dna.charAt(2);
}
This is my code so far but I dont know what to put as my return and I don't know how to call the method from my main method? All I need is to make sure the string "dna" has three characters in it.
The method doesn't return anything as of yet, I really just want to make sure I'm on the right track and this is how I have to restrict the number of characters in my string.
EDIT: Sorry to add one more thing but if I wanted to add a condition to the method, like let's say I already made a boolean method beforehand and wanted to check if the char firstCharacter was true according to the method how would I add it?

I don't know how to call the method from my main method?
Like this:
public static void main(String[] args) {
watsonCrick("ATA");
}
or if the watsonCrick method is in a different class, like this:
public static void main(String[] args) {
OtherClass.watsonCrick("ATA");
}
All I need is to make sure the string "dna" has three characters in it.
You can do this by putting this at the beginning of the watsonCrick method:
if (dna.length() != 3) { throw new IllegalArgumentException(); }

Assing dna variable in Main method and then write just methodName(Parameters) for calling the method in Main. i.e
String dna;
public static void main(String[] args) {
dna = "ATA";
watsonCrick(dna);
}
And if you need to make sure the string has three characters, use this;
public static String watsonCrick(String dna){
int length = dna.length();
if(length == 3) {
return "true";
}
return "false";
}
If you want you can change the return type to Boolen. (True or False)

Java String function can not be called because it's not static

Let me explain further. I have a String function (called stringReversal) that returns a reversed string, it has no errors in the function. But, when I try to print using System.out.println() from the main function, it gives me the error "Can not make a static reference to the non static method stringReversal (string s) from the type StringReverse".
I tried giving my stringReversal a static modifier, but after doing so, it gave me run time errors.
Here's what my code looks like:
public class StringReverse {
public String stringReversal(String s){
if(s == null){
return null;
}
else if(s.length()% 2 == 0){
int size = s.length();
for(int i =0; i<s.length(); i++){
s.replace(s.charAt(i), s.charAt(size));
size--;
if(i == (s.length()/2) || size==0)
break;
}
}
else{
for(int i =0; i<s.length(); i++){
int size = s.length();
s.replace(s.charAt(i), s.charAt(size));
size--;
if(i == ((s.length()/2) +1) || size==0 )
break;
}
}
return s;
}
public static void main(String[] args) {
String str = "Hello";
String rev = stringReversal(str);
System.out.println();
}
}

You have to instantiate your class to call object members, or you need to make your function static, indicating it's not part of object oriented paradigm
In your case you can do
StringReverse sr = new StringReverse();
String rev = sr.stringReversal("hello");
or declare your method differently
public static String stringReversal(String s)
In fact the class name StringReverse itself does not sound like some kind of object, so the second way is preferred impo
The deeper problem you have is the confusion on how Java handle OO and entrance function in general. Java is primarily an OO language so most of the time everything shall be an object or a member of a object. But when you telling the VM to run some java code, there got to be a place to start, which is the main method. There has to be one main method and it must be under some class, but it really has nothing to do with the class that contains it. Within the main method, you either start your OO life by instantiating objects and invoking their members (method 1) or stay in the spaghetti world for a bit longer, by calling other static members as procedures (method 2).

You have two options:
Keep the method non static and then create an instance of your class to call the method:
public static void main(String[] args) {
String str = "Hello";
StringReverse sr = new StringReverse(); // instance of class
String rev = sr.stringReversal(str);
System.out.println(); // just prints a blank line lol...
}
Make the method static (you should do this):
public static String stringReversal(String s) {
// ...
}
public static void main(String[] args) {
String str = "Hello";
String rev = stringReversal(str);
System.out.println(); // just prints a blank line lol...
}
Either way, you have to fix your "run time errors". You can't get around that. If your method doesn't work, keeping it not static won't make it work either.
By the way, I think you meant to do System.out.println(rev); instead of System.out.println();
For the record, here is how to easily reverse a string (both methods work):
public static String stringReversal(String s) {
StringBuffer reverseString = new StringBuffer();
// reverse the string
for (int i = s.length() - 1; i > -1; i--) {
reverseString.append(s.charAt(i));
}
return reverseString.toString();
}
/* using the reverse() method in the StringBuffer class
instead of reversing the string through iterations */
public static String stringReversal2(String s) {
return new StringBuffer(s).reverse().toString();
}

This is happening because your Main method is static, but the class that it's in is not. In order to call a non-static method, you need to create an instance of the class. Alternatively, the method can be made static, but in order to refer to it you need to include the class name in your call (as if to use the class itself like an object containing the method - see below).
There are three solutions to this problem:
Make an instance of the class and call the method from your object (recommended).
make the method static and use StringReverse.stringReversal().
Make the class AND the method static.