無法在Action偵聽器（Jframe）中引用非變量

Question

以下程序的目標是要求用戶輸入一個電阻值，然后程序將為每個數字輸出相應的顏色。 因此，這不包括所有數字。 但是，該程序已完成，我嘗試將JFrame作為額外的東西合並，除了我迷上了如何在動作偵聽器中打印相應的顏色。

該行調用特定的方法，然后3位數字繼續打印顏色，除了如何將其和其余代碼合並到JFrame和/或ActionListener中。 行System.out.println（array3 [i]）; /

當嘗試在操作偵聽器中簡單地打印顏色值“無法引用非最終變量”時，我確實收到錯誤。

我嘗試過在線查看各種教程，甚至Java API和指南，這些都無濟於事。 總的來說，我似乎不知道如何將已經寫入JFrame的代碼合並，無論這是一個乏味的過程，還是我願意與公司合作，並且非常感謝您對如何解決這一困境的一些見解。

import java.io.*;
import javax.swing.*;
//import javax.swing.JFrame;
//import javax.swing.JLabel;
//import javax.swing.JButton;
//import javax.swing.JPanel;
//import javax.swing.JTextField;
import java.awt.event.*;


public class test extends JFrame
{
  public static void main (String [] args) throws IOException
  {
    BufferedReader myInput = new BufferedReader (new InputStreamReader (System.in));


    //calling variables
    String input;
    int numInput;

    JLabel l = new JLabel("Hello and welcome to the Program (Press the button to start the instructions");
    //l.setAlignmentX(0);
    // l.setAlignmentY(0);

    //calling arrays
    int [] array = new int [5];
    int [] array2 = new int [3];
    String [] array3 = new String [3];
    String[] colours = {"black", "brown", "red", "orange", "yellow", "green", "blue", "violet", "gray", "white"};


    JFrame f = new JFrame("Hello JFrame");
    f.setSize(500,500);
    //f.getContentPane().setBackground(Color.CYAN);
    f.add(l);
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setVisible(true);

    //JTextField t = new JTextField(16);


    JPanel p = new JPanel ();
    JButton b = new JButton("Press me") ;
    // b.setAlignmentX(0);
    // b.setAlignmentY(0);

    b.addActionListener(new ActionListener(){
      public void actionPerformed (ActionEvent e) {
        JOptionPane.showMessageDialog(null,"In the following program you (The user!) will input a number of a resistor value \nThe program will pass the information into methods and then proceed to print out \nThe coorelating colors (Press the button to be asked for input)");
        int number = Integer.parseInt(JOptionPane.showInputDialog("Please enter the resistor value"));


        JOptionPane.showMessageDialog(null, "The Colors are : " + (array3[i] + "\n" ));



      } 

    });

    p.add(b);
    p.add(l);
    //p.add(t);
    f.add(p);


    System.out.println("Hello and welcome to the Program (Press any key to con't)");
    input = myInput.readLine ();

    System.out.println("In the following program you (The user!) will input a number of a resistor value");
    System.out.println("The program will pass the information into methods and then proceed to print out");
    System.out.println("The coorelating colors (Press any key to be asked for input)");
    input = myInput.readLine();

    System.out.println("Enter a resistor value (Note that resistors can only acount to 4 decimal places");
    input = myInput.readLine ();
    numInput = Integer.parseInt (input);

    //colours for values
    array2 = values(array, input, colours);
    for(int i = 0 ; i < 3; i++){
      array3[i] = digitColours(array2[i], colours);
      System.out.println(array3[i]);// prints colours for values
    }


    //prints 4th colour for multiplier
    System.out.println(decimalPlaces(input, colours));

  } 

  public static int[] values (int [] digit, String num, String[] colours)
  {

    String holder;
    double numHolder;
    int lengthOfInput;
    int holder2;

    //tollerance
    holder = num.substring(3,4);
    digit[3] = Integer.parseInt(holder);
    holder2 = Integer.parseInt(num);
    // checks to see if above 5
    if(digit[3] < 5){
      digit[3] = digit[3]/holder2 * 100;
    }
    else if(digit[3] > 5){
      digit[3] = 10 - digit[3];
      digit[3] = digit[3]/holder2 * 100;
    }
    System.out.println(digit[3]);

    //Rounding of the input
    lengthOfInput = num.length() - 3;
    numHolder = Double.parseDouble(num);
    numHolder = numHolder/(Math.pow(10,lengthOfInput));
    numHolder = (int)(Math.round(numHolder)+0.5);

    // first three digits
    for(int i = 0; i < 3; i++){
      holder = num.substring(i,i+1);
      digit[i] = Integer.parseInt(holder);
    }

    //print out for information
    /*System.out.println("The first digit is rounded to:" + (int)digit[0]);
     System.out.println("The second digit is roudned to:" + (int)digit[1]);                   
     System.out.println("The third digit is roudned to:" + (int)digit[2]);  */
    /* */
    return new int[] {digit[0], digit[1],digit[2],digit[3]} ;// return
  }


  public static String digitColours(int decimalPlace, String[] colours){
    //calling additional variables
    String answer;
    answer = colours[decimalPlace];
    return answer;
  }


  //method to find the multiplier
  public static String decimalPlaces(String input, String[] colours){
    //calling additional variables
    int length = input.length();
    String answer;

    length = length - 3;
    answer = colours[length];

    return answer;
  }
} 

Answer 1

在Java中，您不能引用匿名內部類中的非最終變量。 您嘗試在ActionListener匿名實現中訪問array3 。 您可以簡單地將array3更改為final，即：

final String [] array3 = new String [3];

另外，要打印數組的內容，可以使用Arrays.toString() ：

JOptionPane.showMessageDialog(null, "The Colors are : " + (Arrays.toString(array3)));