How do I use a variable that has been returned

[jwl]

package test;

public class Test {
    
    public Test(){
        callReturnValues();
    }
    
    public int[] return1() {
        int [] values = {30, 49, 43, 30, 60};
        return values;
    }
    
    public void callReturnValues() {
        // call values
        // print out values
    }
    public static void main(String[] args) {
        new Test();
    }
}

[pbrockway2]

The only method that returns anything there is return1(). I'm not quite sure where you want to use what it returns. In callReturnValues() perhaps?

public void callReturnValues() {
    int[] values = return1();
    // print out values
}

As shown the first order of business is to assign the returned value to some variable. Then you can do whatever you like with it. (And whatever you do like to do with it should be reflected in the method's name: callReturnValues() is very nondescriptive.)

Or perhaps you want the magic to happen in main()?

public static void main(String[] args) {
    Test test = new Test();
    int[] values = test.return1();
    // do something with values
}

Notice again a variable (test) is used and assigned to using what the "new" operator returns.

Or perhaps, something else...?

[jwl]

I think I got I needed with that now I have this.

package test;

public class Test {
    
    public Test(){
        callReturnValues();
    }
    
    public int[] return1() {
        int[] returnValues = {30, 49, 43, 30, 60};
        return returnValues; 
    }
    
    public void callReturnValues() {
        int[] returnValues = return1();
        System.out.println(returnValues[3]);
        // more stuff with returnValues[]
    }
    public static void main(String[] args) {
        new Test();
    }
}

Thanks

[jwl]

OK, That worked for that simpler program. Now I am running into a little more technical difficulties.

package test;

import java.io.File;
import java.io.IOException;
import java.util.Scanner;

public class Test {
    private Scanner read;
   private int numData;
    
   public Test() { // constructor which runs the methods
       openFile();
       readInputFile();
       closeFile();
       testMethod();
   }
    // Open File
   private void openFile() {
       try {
           read = new Scanner(new File("file.txt")); // reading integers from a file
       }
       catch (IOException e) {
           System.out.println("Could not open file input");
       }
   }
   
   //Close File
   private void closeFile() {
       read.close();
   }
  
   //Read File and Store it in an array of size numData
   private int[] readInputFile() {
       numData = read.nextInt(); // Creating size of array from file
       read.nextLine();
       int[] data = new int[numData]; //Storing integers in an array
        for (int i = 0; i < numData; i++) {
            data[i] = read.nextInt();
            //System.out.printf("%s\n", data[i] + " array item: " +  i); //testing all data is read from file
       }
       return data;
   }
   
   public void testMethod() {
       int[] data = readInputFile();
       System.out.println(data[9]); // Testing that data from readInputFile() has transfered correctly 
   }
    
    public static void main(String[] args) {
        new Test(); // call constructor
    }
}

This is what happens when I run it:

Exception in thread "main" java.lang.IllegalStateException: Scanner closed
followed by more at ..... errors

When you take the testMethod out and uncomment the test string in the readInputFile() as well as delete the test method call in the constructor the program runs fine.

[SJF]

  public void testMethod() {
       int[] data = readInputFile();  //You've already closed the file here

Doing all this in your constructor may not be what you ultimately want.... look at what pbrockway2 suggested, much cleaner.

[SJF]

  public void testMethod() {
       int[] data = readInputFile();  //You've already closed the file here

Doing all this in your constructor may not be what you ultimately want.... look at what pbrockway2 suggested, much cleaner.

...
run closeFile() after testMethod() ;)

Don't run readInputFile() in constructor ... it's called by testMethod(), Scanner will already be at the end of file by the time testMethod() tries to get results.

[jwl]

Doing all this in your constructor may not be what you ultimately want.... look at what pbrockway2 suggested, much cleaner.

...
run closeFile() after testMethod() ;)

All of that for a cut and paste error. Thank you guys.

[SJF]

Occam's razor - Wikipedia, the free encyclopedia

[DarrylBurke]

Terminology nitpick: methods can return values, not variables. The value returned by a method may be assigned to a variable.

db