Java无法识别循环外的循环中创建的对象

Question

    String nameFromFile;
    String colorFromFile;
    int capacityFromFile;
    int currentCountFromFile;


    while(inputFile.hasNextLine()){
        nameFromFile = inputFile.next();
        colorFromFile = inputFile.next();
        capacityFromFile = inputFile.nextInt();
        currentCountFromFile = inputFile.nextInt();

        MarbleSackOwner owner1 = new MarbleSackOwner(nameFromFile, colorFromFile,
                                    capacityFromFile, currentCountFromFile);


        nameFromFile = inputFile.next();
        colorFromFile = inputFile.next();
        capacityFromFile = inputFile.nextInt();
        currentCountFromFile = inputFile.nextInt();

        MarbleSackOwner owner2 = new MarbleSackOwner(nameFromFile, colorFromFile,
                                    capacityFromFile, currentCountFromFile);

        nameFromFile = inputFile.next();
        colorFromFile = inputFile.next();
        capacityFromFile = inputFile.nextInt();
        currentCountFromFile = inputFile.nextInt();

        MarbleSackOwner owner3 = new MarbleSackOwner(nameFromFile, colorFromFile,
                                    capacityFromFile, currentCountFromFile);

        nameFromFile = inputFile.next();
        colorFromFile = inputFile.next();
        capacityFromFile = inputFile.nextInt();
        currentCountFromFile = inputFile.nextInt();

        MarbleSackOwner owner4 = new MarbleSackOwner(nameFromFile, colorFromFile,
                                    capacityFromFile, currentCountFromFile);

    }
    String output = "Owners after creaton based on file read \n";
    output += "Owner1: " + owner1 + "\n";
    output += "Owner2: " + owner2 + "\n";
    output += "Owner3: " + owner3 + "\n";
    output += "Owner4: " + owner4 + "\n";

    output += "owner1's name is " + owner1.getName() + "\n";
    output += "like I said, owner1 has " + owner1.howManyMarbles() + 
                " marbles in his sack.\n";
    output += "So lets take one away from him.\n";
    owner1.removeMarbles(1);
    output += "so now we see that he has " + owner1.howManyMarbles() +
                " in his sack.\n";
    output += "so lets give the darn thing back to him now.\n";
    owner1.addMarbles(1);
    output += "so now we see that he has " + owner1.howManyMarbles() +
                " in his sack.\n";

    //mess with owner4
    output += "so, maybe " + owner4.getName() +
                " has lost a marble or two, so lets give him back one.\n";
    owner4.addMarbles(1);
    output += "So now we see that he has " + owner4.howManyMarbles() + 
                " marbles in his sack.\n\n";

    //test class method
    output += "the owner with the most marbles is " +
                bigOwner(owner1, owner2, owner3, owner4);

    //results
    JOptionPane.showMessageDialog(null, output, TITLE_BAR, JOptionPane.INFORMATION_MESSAGE);

}//main

I am getting errors on every call to a owner object outside of the while loop saying "owner# cannot be resolved to a variable". if I declare the objects before the loop, I get a duplicate object error on the objects created within the loop. I'm not quite sure how to make this work.

Answer 1

You have declared and initialized your variables owner1, owner2, owner3 at the same time inside while loop. What you can do is, First declare and initialize the variable before (outside) loop and create owner objects within while loop like this:

MarbleSackOwner owner1 = null;
...
while(..){
...
owner1 = new MarbleSackOwner(nameFromFile, colorFromFile,
                                    capacityFromFile, currentCountFromFile);
...
}

Similarly do this action for other two owner variables. Read through scope of variables for better understanding.

http://www.java-made-easy.com/variable-scope.html

If you are going to create multiple owner objects then you can create a list object above your while loop and add the owner objects to that list and retriev the added objects from your list while printing the values.

Answer 2

If you want access to these variables in and out of the while, you need to declare them outside. In your case, these variables are know only inside the while cause that's where they have been declared. Try reading up on variable scopes.

Try something like this:

MarbleSackOwner owner1 = new MarbleSackOwner(string.Empty, string.Empty, 0, 0),
owner2 = new MarbleSackOwner(string.Empty, string.Empty, 0, 0),
owner3 = new MarbleSackOwner(string.Empty, string.Empty, 0, 0),
owner4 = new MarbleSackOwner(string.Empty, string.Empty, 0, 0);    

while(inputFile.hasNextLine()){
        nameFromFile = inputFile.next();
        colorFromFile = inputFile.next();
        capacityFromFile = inputFile.nextInt();
        currentCountFromFile = inputFile.nextInt();

        owner1 = new MarbleSackOwner(nameFromFile, colorFromFile,
                                    capacityFromFile, currentCountFromFile);


        nameFromFile = inputFile.next();
        colorFromFile = inputFile.next();
        capacityFromFile = inputFile.nextInt();
        currentCountFromFile = inputFile.nextInt();

        owner2 = new MarbleSackOwner(nameFromFile, colorFromFile,
                                    capacityFromFile, currentCountFromFile);

        nameFromFile = inputFile.next();
        colorFromFile = inputFile.next();
        capacityFromFile = inputFile.nextInt();
        currentCountFromFile = inputFile.nextInt();

        owner3 = new MarbleSackOwner(nameFromFile, colorFromFile,
                                    capacityFromFile, currentCountFromFile);

        nameFromFile = inputFile.next();
        colorFromFile = inputFile.next();
        capacityFromFile = inputFile.nextInt();
        currentCountFromFile = inputFile.nextInt();

        owner4 = new MarbleSackOwner(nameFromFile, colorFromFile,
                                    capacityFromFile, currentCountFromFile);

    }