Java方法安排，运行时错误

Question

我已经编写了一个程序，根据用户选择要放入哪个列，显示放入板中的令牌。我遇到运行时错误

java.lang.StringIndexOutOfBoundsExcepti… String index out of range: 42
    at java.lang.String.substring(Unknown Source)
    at A1Program.extractRow(A1Program.java:83)
    at A1Program.start(A1Program.java:19)
    at A1Application.main(A1Application.java:11…
    at sun.reflect.NativeMethodAccessorImpl.inv… Method)
    at sun.reflect.NativeMethodAccessorImpl.inv… Source)
    at sun.reflect.DelegatingMethodAccessorImpl… Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at edu.rice.cs.drjava.model.compiler.JavacC… 

当我运行这个程序时，我有点不知道我可能出了什么问题

我的代码是：

public class A1Program {

    public void start() {

        String inputString = "XOXOXOO X XXO X OXO ";
        boolean gameOver = false;

        String tokens = inputString;

        while (!gameOver) {
            int column = columnResult();
            tokens = enterToken("X", tokens, column); 
            System.out.println(tokens);
            displayBoard(extractRow(5, tokens));
            displayBoard(extractRow(4, tokens));
            displayBoard(extractRow(3, tokens));
            displayBoard(extractRow(2, tokens));
            displayBoard(extractRow(1, tokens));
            displayBoard(extractRow(0, tokens));
            System.out.println("---------------");
        }
    }

    private int columnResult(){
        System.out.println("Enter column for X:");
        String keyInput = Keyboard.readInput();
        int column1 = Integer.parseInt(keyInput);
        return column1;
    }
    private String enterToken(String tokenSymbol, String inputString, int column){
        String columnEdit = inputString.substring(column*6-6,column*… 

        String columnEdit1 = columnEdit.trim();
        String columnEdit2 = columnEdit1+tokenSymbol+" ";
        String columnEdit3 = columnEdit2.substring(0,6);
        String start = inputString.substring(0,column*6-6);
        String end = inputString.substring(column*6);

        System.out.println(start);
        return start+tokenSymbol+end;
    }

    private String extractRow(int row, String tokens) {
        String rowString1 = tokens.substring(row, row + 1);
        String rowString2 = tokens.substring(row + 6, row + 7);
        String rowString3 = tokens.substring(row + 12, row + 13);
        String rowString4 = tokens.substring(row + 18, row + 19);
        String rowString5 = tokens.substring(row + 24, row + 25);
        String rowString6 = tokens.substring(row + 30, row + 31);
        String rowString7 = tokens.substring(row + 36, row + 37);

        return "|" + rowString1 + "|" + rowString2 + "|"
                + rowString3 + "|" + rowString4 + "|" + rowString5
                + "|" + rowString6 + "|" + rowString7 + "|";

    }

    private void displayBoard(String extractRow) {

        System.out.println(extractRow);

    }
}

Answer 1

跟踪中的以下行：java.lang.String.substring(Unknown Source)表示问题出在tokens.substring()

这是因为令牌的长度小于您试图提取的子字符串。你可以打印代币的长度，自己检查