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Am I returning the correct value from my method & am I writing it correctly?

I'll preface my question with the statement that I am very new to Java, so I apologise if my code is totally disgusting to read.
What I'm trying to do: I'm writing a program that takes two integers from the user, a low value and a high value, and sends both integers to two different methods. Method #1 has a simple for loop and should print out all of the numbers between the lowest number and the highest number that are multiples of 3 or 5, and Method #2 does the same except for numbers that are multiples of 3 or 5 it also checks if that number is also a multiple of 6 and, if so, it prints the number and an asterisk next to it.
What I'm having trouble with: I'm pretty stumped on what I need to return from my methods & how to return anything at all. This is the first time I've worked on a method properly (just moved up from "Hello World) and from what I can see I don't really need to return anything at all. All the code that I've put in my methods pretty much complete the program, so I thought maybe returning the integers I sent would be enough, apparently it's not. So, without further ado, here's my code.
The Error:
javac BonusQ.java
.\MethodOne.java:19: error: illegal start of type
return(int lowestRange, int highestRange);
^
.\MethodTwo.java:36: error: illegal start of type
return(int lowestRange, int highestRange);
^
The Main:
import java.util.Scanner;
public class BonusQ
{
public static void main(String [] args)
{
Scanner scan = new Scanner(System.in);
int lowestRange = 0;
int highestRange = 0;
System.out.println("Enter the lowest integer in your range");
lowestRange = scan.nextInt();
System.out.println("Enter the highest integer in your range");
highestRange = scan.nextInt();
MethodOne.NoAsterisk(lowestRange, highestRange);
MethodTwo.Asterisk(lowestRange, highestRange);
}
}
MethodOne:
public class MethodOne
{
public static int NoAsterisk(int lowestRange, int highestRange)
{
for(int i = lowestRange; i <= highestRange; i++)
{
if (i%5 == 0)
{
System.out.println(i);
}
else if (i%3 == 0)
{
System.out.println(i);
}
}
}
return(int lowestRange, int highestRange);
}
MethodTwo:
public class MethodTwo
{
public static int Asterisk(int lowestRange, int highestRange)
{
for(int i = lowestRange; i <= highestRange; i++)
{
if (i%5 == 0)
{
if (i%5 == 0 && i%6 == 0)
{
System.out.println(i + "*");
}
else
{
System.out.println(i);
}
}
else if (i%3 == 0)
{
if (i%3 == 0 && i%6 == 0)
{
System.out.println(i + "*");
}
else
{
System.out.println(i);
}
}
}
}
return(int lowestRange, int highestRange);
}
Sorry if the post is a bit beefy to read, I just find that adding my thoughts on the code might help you explain to me what's going wrong, seeing as you may not know the extent of my incompetence :)
Thanks in advance.

Ok, Classes have members.
Members are either some variables or arrays of variables
and the methods of a class.
So you got
public class MyMethod
{
public static int Asterisk(int loRange, int hiRange)
{
// Do magic let's make a sum for this example
// You enter loRange and hiRange (you defined it above)
return loRange + hiRange // Here the method returns a result
}
}
// So then....
public static void main(String [] args)
{
// WHATEVER IS IN HERE RUNS ALWAYS FIRST.
z = Asterisk(1,2); // 1 and 2 is lo and hi range values ;)
// Z has a value of 3 now because Asterisk(1,2) returns 1 + 2
}
See how this works?
Now this works because you use the static definition (meaning there must not be an instance of MyMethod created first to use the method. It's not wrong, but if you can make a program do things with class instances, you better do it that way.
You make an instance of a class, this is called an object, using a special method. This method has the exact name of the Class and constructs an instance of it.
You should study now about constructors, abstract classes etc etc.
I can't say you do it wrong or right either. It is about what the program is all about and you should study the scope for variables and methods, and the encapsulation concept of Object Oriented Programming.
Using only static methods, goes against encapsulation principle, it is possibly wrong but I can't tell for sure.
I hope this helped you and gave you a good direction to go on with your study.
PS:
To return multiple results, you should return an array of variables, not just a variable.
You can also return nothing and just have it do the job to a needed array. This FORCES you though to make this array public. (Not a good practice)
Finally if multiple value returns are needed to just print them on the console... well, just do it in the method, no need to return anything really.

You don't need to return anything, being that the methods are printing out all the values.
You can change them into void methods, for example:
public static void asterisk(int lowest, int highest) {
//loops and if statements
//no return statement!
}
The code in the methods will run and voila, you are done!
EDIT: That being said, there's a lot more than can be done to make this code more Java-like, but for now this will work.

mmmmm...you can return types, and (int lowestRange, int highestRange) its not a type. Look at the method definition
public static int Asterisk(int lowestRange, int highestRange)
the return type is declared as int, so you should return an int value. You can do something like
return lowestRange;
return 1;
with that in consideration, the error should dissapear. The question is, why do you need to return a value? From what i've read, your methods are supose to print stuff, not to return stuff...

The return statements are out of the method. You have to put them before the close method brackets.
public class MyClass{
public int sum (int a, int b){
return a + b;
} // The return have to be before this brackets
}

I get a compile time error when accessing an ArrayList with a new method

I am attempting to access an ArrayList that was created in a different method within the same class. The scanner method pulls in data from a text file. The text file data appears this way: 123 12 1 43, with line breaks...
Currently, my method works to pull in the data, but does not compile after that method ends. I originally had the entire code within the same method and it worked fine. But I'd like to return the largest value by creating a new method within this class, and then create a tester class that will access this new method. Here is my existing code. Or if there is a better solution. I'm all ears.
public class DataAnalyzer {
public DataAnalyzer(File data) throws FileNotFoundException
{
List<Integer> rawFileData = new ArrayList<>();
FileReader file = new FileReader("info.txt");
try (Scanner in = new Scanner(file)) {
while(in.hasNext())
{
rawFileData.add(in.nextInt());
}
}
}
public int getLargest(rawFileData){
int largest = rawFileData.get(0);
for (int i = 1; i < rawFileData.size(); i++){
if (rawFileData.get(i) > largest)
{
largest = rawFileData.get(i);
}
}
for (Integer element : rawFileData){
if (element == largest)
{
System.out.print("This is the Largest Value: ");
System.out.print(element);
}
}
}
}

Your main issue is with your method declaration. It needs a type parameter:
public int getLargest(List<Integer> rawFileData)
Note the List<Integer>.
Now, there is already a method for this in the Collections utility class. You would do well to look over that link in detail - there are many useful methods there. To get the highest element from a Collection of Objects that have a natural order (such a Integer). For example
int largest = Collections.max(rawFileData)
So your method can be reduced to:
public int getLargest(List<Integer> rawFileData)
return Collections.max(rawFileData);
}
You need to think over your logic much more carefully before you begin to write code, for example, your first loop is good:
int largest = rawFileData.get(0);
for (int i = 1; i < rawFileData.size(); i++){
if (rawFileData.get(i) > largest)
{
largest = rawFileData.get(i);
}
}
You do exactly what any programmer would do. But then, instead of returning the largest when you find it, you for some reason loop again:
for (Integer element : rawFileData){
if (element == largest)
{
System.out.print("This is the Largest Value: ");
System.out.print(element);
}
}
Ask yourself what does this do? You have a List of, say, apples. You look at each one and compare them - finding the largest apple. You now have the largest apple in the List. You then loop over the List again looking for an apple that matches the apple you have already found. Why do this?
Further, you never return from the method. Your method is declared as returning an int; but you never do.

The missing type in your method definition is the problem here.
Change the method definition from
public int getLargest(rawFileData) {
....
}
to
public void getLargest(List<Integer> rawFileData) {
....
}
And the second for loop in the method is unnecessary. The largest integer is already stored in the variable "largest" and you can print it after the first for loop.

Array in Method Header: error ']' expected (Java)

I'm quite new to arrays and methods, and I've been seeing this error recurring through several programs: error '[' expected.
In each occasion, it seems to correct itself as I adjust something else, but in this particular case, I am completely stumped.
By the way, I am using several methods and arrays to create a quiz (before you ask, yes, this is an assignment and I agree, a list is a better way to handle this data - but that is not an option).
It is possible that I am not passing the arrays correctly between methods, as I'm a little muddy on that process. From my understanding, in order to send/receive (i.e. import/export) an array or other variable between methods, I must declare that variable/array in the method header parameters.
import java.util.Scanner;
public class H7pseudo
{
public static void main(String[] args)
{
//call getAnswerkey method
getAnswerkey(answerkey[i]);
//call getAnswers method
getAnswers(answers[i]);
//call passed method? necessary or no?
boolean passed = passed(answerkey[i], answers[i], qMissed[i], points);
//Print results of grading
if (passed)
{
System.out.println("Congratulations! You passed.");
}
else
{
System.out.println("Try again, sucka. You FAILED.");
}
//call totalPoints
totalIncorrect(points);
//call questionsMissed
questionsMissed(qMissed[i]);
}
//get answer key (create answerkey array & export)
public static void getAnswerkey(answerkey[i])
{
//create answerkey array here
char[] answerkey;
//determine number of questions (indices)
answerkey = new char[20];
//input values (correct answers) for each index
//for our purposes today, the answer is always 'c'.
for (int i = 0; i <=20; i++)
{
answerkey[i] = 'c';
}
}
//get student answers (create answers array & export)
public static void getAnswers(answers[i])
{
//initialize scanner for user input
Scanner scan = new Scanner(System.in);
//create answer array here
char[] answers;
//determine number of questions (indices)
answers = new char[20];
//prompt for user input as values of each index
for (int i = 0; i <= 20; i++) {
answers[i] = scan.nextChar();
}
}
//grade student answers (import & compare index values of arrays:answers&answerkey
//create & export qMissed array
public static boolean passed(answerkey[i], answers[i], qMissed[i], points)
{
int points = 0;
//create new array: qMissed
boolean[] qMissed;
//determine number of questions to be graded
qMissed = new boolean[20];
//initialize values for array
for (int i = 0; i <= 20; i++) {
qMissed[i] = false;
}
//cycle through indices of answerkey[i] & answers[i];
for (int i = 0; i =< 20; i++)
{
if (answers[i] == answerkey[i])
{
correct = true;
points = points+1;
qMissed[i] = true;
}
else {
qMissed[i] = false;
}
}
//evaluate whether or not the student passed (15+ correct answers)
if (points >= 15)
{
passed = true;
}
else
{
passed = false;
}
return passed;
}
public static void totalIncorrect(points)
{
int missed = 20 - points;
System.out.println("You missed " + missed + " questions.");
}
public static void questionsMissed(qMissed[i])
{
// for each index of the array qMissed...
for (int i = 0; i < qMissed.length; i++)
{
//...print correct and false answers.
system.out.println(i + ": " + qMissed[i] + "\n");
}
}
}

You can't define array size in the method signature, in Java.

public static void getAnswerkey(answerkey[i])
You can't put anything inside the [] in a method declaration. Also, you have to mention the type:
public static void getAnswerKey(char[] answerkey)
This is not the only reason your code won't work as intended, but I'll leave the rest as part of the exercise.

Look at your method definitions:
public static void questionsMissed(qMissed[i])
This is wrong. You should define the type of the variable and it should not contain [i] like an element of an array. It should be something like this:
public static void questionsMissed(int qMissed)
Or if you want to pass the array, write it like this:
public static void questionsMissed(int[] qMissed)
Apart of this, there are other several errors in your code:
getAnswerkey(answerkey[i]); //answerkey is not defined
getAnswers(answers[i]); //answers is not defined
It would be better if you start reading a Java tutorial first.

I want to vote up Luiggi's answer, but I don't have enough reputation to do that :)
Congrats, cordivia, on getting started with Java!
Here is how an array is declared:
type[] arrayName = new type[numberOfElements]
For example, you did this right in your method definition for getAnswerkey():
char[] answerkey;
answerkey = new char[20];
The part in the method definition inside the parentheses defines the kind of data the method is willing to accept from the outside. So if you don't need to put something into the method to get something out of it, you don't need to put anything in the parentheses. Define the method like this:
getAnswerkey() {
...But that's not the whole story. If you want to get something out of the method, it needs to have a return type as well. A return type is what you're gonna get out of the method when the method's done doing it's magic. For example, if you want to get an int array out of a method you would do something like this:
public static int getTheInteger() {
Since you want an array of chars from the method, you'll want to do something like this:
public static char[] getAnswerkey() {
So that's how you get a method to give you something back. If don't want anything back, you put void:
public static void noMarshmallows() {
Now, when you use the method, you're gonna need to do something with what it gives you, or it did all that work for nothing. So you need to store the return value in a variable when you call the array (calling methods is what you've been doing in main). You know how to store something in a variable. You use the '=' operator:
int myVeryFavoriteNumber;
myVeryFavoriteNumber = 5;
So, you do the same thing when you're getting something out of an array. You assign the return value to a variable. If you want to do this with an array, do this:
int[] myFavs;
myFavs = getMyFavoriteNumbers();
Same with chars:
char[] answerKey;
answerKey = getAnswerKey();
Voila! Your answer key is now right out in the open for the rest of main to see :)
Now, if you want to put something into a method and have it do something with what you put in, you define a parameter. You know how this works. It's just like declaring a variable, and that's exactly what it is. Parameters go in the parentheses and only the method using the parameter sees that variable name (it's local). Something like this:
public static void plusOneToAll (int[] numbers) {
for (int i = 0; i < numbers.length; i++) {
numbers[i] = numbers[i] + 1;
}
}
Notice int[] numbers in the parentheses. The type being passed in is int[] or integer array. numbers is just the parameter name. It functions just like a variable, but it is declared locally (inside the parentheses) and use locally (inside the method). So, if you wanted to compare the answers from two arrays and return the number of matches (like a total score for instance), you would do something like this:
public static int getTotalScore (char[] correctAnswers, char[] userAnswers) {
int totalScore = 0;
for (int i = 0; i < correctAnswers.length; i++) {
if (userAnswers[i] == correctAnswers[i]) {
totalScore = totalScore + 1;
}
}
return totalScore;
}
Notice the return type: int (written before the method name). Inside the array I'm using the variable totalScore to keep track of the number of times the answers match. The method takes two char arrays from the outside and uses them on the inside. Finally, I return an int: totalScore. That kicks the value of totalScore back out to whatever called it (main).
If I might add one last thing: Do yourself a favor and go pick up a copy of Head First Java. It's hard to find a good tutorial online and Java textbooks are just plain boring. The Head First series are kind of like coloring books for adults.
Best of luck!

Find and print the product of all the entries in array

Okay I have tried to write a simple Java code in BlueJ, that finds and prints the product of all the entries in data such as if data is {1,2,3,4} then the result will be 24.
And my code is below:
public class Product {
public static int[] product(int[] a) {
int [] s = new int[a.length];
for (int i =0; i< a.length; i++)
s[i] = a[i]*a[i];
return s; //the definition of your method...
}
public static void main(String[] args) {
//calling the method to seek if compiles
int[] results = Product.product(new int[] { 1,2,3,4 });
//printing the results
System.out.println(java.util.Arrays.toString(results));
}
}
The above code is giving me the square of each number, which is not what I want to have, somehow I have modify the code that the result will be 24 but I couldn't figure it out, anyone knows how to do it?

First of all, if you are first writing Java it is important to know that variable, function and class names are quite important. Please note that having Product.product() is not a good idea, since the function name is almost the same as the class name. Anyway, regarding your code. Your code is indeed returning the square of your input, what you would want is the following:
public class Product {
public static int getProduct(int[] input) {
int total = 1;
for (int v : input) {
total *= v;
}
return total;
}
}
This will return an integer value with the product of your input array. This also uses a for-each loop instead of a regular for-loop for readability. Also you don't need the index in this case. Good luck with it!

First, your product method needs to return an int rather than an int [].
You need to maintain the product as a variable. You can set it to 1 initially, and then multiply it by each element of the a array in turn; then you just return this value.

Lexicographic quicksort algorithm

My professor gave me a code for the methods to be used in sorting an array of names lexicographically, but I have no idea how what to write inside the main class to show that the program works. I am very new to java, so please if you know how to do this could you write it as simple as possible for me to understand it. Thanks in advance.
This is are the classes
public class quicksort_class {
int[] array1 = new int[11];
public quicksort_class(int[] w)
{
array1 = w;
}
private static void sort(String[] string, int leftlimit, int rightlimit) {
if (rightlimit > leftlimit)
{
int midpoint = partitionstep(string, leftlimit, rightlimit);
sort(string, leftlimit, midpoint - 1);
sort(string, midpoint, rightlimit);
}
}
public static int partitionstep(String[] string, int leftlimit, int rightlimit)
{
String midpoint = string[rightlimit];
int lpointer = leftlimit;
int rpointer = rightlimit;
String temp = "";
while(string[lpointer].compareTo(midpoint) <= 0)
{
lpointer = lpointer ++;
}
while(string[rpointer].compareTo(midpoint) > 0)
{
rpointer = rpointer --;
}
if(lpointer > rpointer)
{
temp = string[lpointer];
string[lpointer] = string[rightlimit];
string[rpointer] = temp;
System.out.println(string);
}
while(lpointer < rpointer)
{
temp = string[lpointer];
string[lpointer] = string[rightlimit];
string[rightlimit] = temp;
}
return lpointer;
}
}
This is the main class (as you can see I have no idea what to write)
package quicksort;
public class Quicksort {
public static void main(String[] args) {
}
}

Write something that sets up an array of strings and calls sort against it, then prints out the results or checks them against a known good result.
Ideally, write something which does this repeatedly, with particular emphasis on checking unusual combinations (already sorted or sorted in reverse, null in the array, same value appearing several times or all values being identical...)
If you want to go beyond that, you need to dig into the code to understand its edge cases and specifically test those, and/or do a "code coverage" analysis (there are tools to help with that) to make sure all parts of the code have been exercised.

Assume the algorithm of sort method is correct:
1. If the main method is within the body of quicksort_class, you can directly call the sort method as sort(arrayToBeSorted, 0 , arrayToBeSorted.length-1). And the arrayToBeSorted should ordered lexicographically after your call. You can check that to confirm.
2. If the main method is in other class, as your main method currently, you need to at least change the private prefix of sort method to public, and call quicksort_class.sort(arrayToBeSorted, 0 , arrayToBeSorted.length-1).
Some tips:
1. Private prefix of method definition means this method can only be called inside current class body.
2. Static prefix of method definition means you should call this method via class name directly, instead of via a instance of class.
By the way, can you provide what the array1 attribute stands for? I don't get why it's there.