Question

我收到错误，说编译器找不到我的变量“complexArray”，但我不知道为什么。如何修复程序以便返回从文件中读取的复数数组？

public static Complex[] parseFromFile(String fileName) {
    int numOfComplex = 0;
    try {   
        Scanner sc = new Scanner(new File(fileName));
        String firstLine = sc.nextLine();
        firstLine = firstLine.trim();
        numOfComplex = Integer.parseInt(firstLine);
        Complex[] complexArray = new Complex[numOfComplex];
        for (int i = 0; i < numOfComplex; i++) {
            String nextLine = sc.nextLine();
            nextLine = nextLine.trim();
            complexArray[i] = parseComplex(nextLine);
        }
    }
    catch(Exception e) {
    }
    return complexArray;
}

Answer 1

您的complexArray变量在try {}范围内声明。在try语句之前声明它。

Complex [] complexArray = null;

Answer 2

将tryArray语句放在try {}语句中

public static Complex[] parseFromFile(String fileName) {
int numOfComplex = 0;
try {   
    Scanner sc = new Scanner(new File(fileName));
    String firstLine = sc.nextLine();
    firstLine = firstLine.trim();
    numOfComplex = Integer.parseInt(firstLine);
    Complex[] complexArray = new Complex[numOfComplex];
    for (int i = 0; i < numOfComplex; i++) {
        String nextLine = sc.nextLine();
        nextLine = nextLine.trim();
        complexArray[i] = parseComplex(nextLine);
    }
 return complexArray;
}
catch(Exception e) {
}

}

Answer 3

因为在complexArray块中声明了try，所以一旦try块内的执行完成，complexArray就超出了范围。

      public static Complex[] parseFromFile(String fileName) {
        int numOfComplex = 0;
        try {   
            Scanner sc = new Scanner(new File(fileName));
            String firstLine = sc.nextLine();
            firstLine = firstLine.trim();
            numOfComplex = Integer.parseInt(firstLine);
            Complex[] complexArray = new Complex[numOfComplex];
            for (int i = 0; i < numOfComplex; i++) {
                String nextLine = sc.nextLine();
                nextLine = nextLine.trim();
                complexArray[i] = parseComplex(nextLine);
            }
        } //<<<=== scope of `complexArray` ends here
        catch(Exception e) {
        }
        return complexArray;
    }

试试这个

      public static Complex[] parseFromFile(String fileName) {
        int numOfComplex = 0;
        Complex[] complexArray;
        try {   
            Scanner sc = new Scanner(new File(fileName));
            String firstLine = sc.nextLine();
            firstLine = firstLine.trim();
            numOfComplex = Integer.parseInt(firstLine);
            complexArray = new Complex[numOfComplex];
            for (int i = 0; i < numOfComplex; i++) {
                String nextLine = sc.nextLine();
                nextLine = nextLine.trim();
                complexArray[i] = parseComplex(nextLine);
            }
        } 
        catch(Exception e) {
        }
        return complexArray;
    } //<<<=== scope of `complexArray` ends here

Answer 4

从@hemanth继续

public static Complex[] parseFromFile(String fileName) {
        int numOfComplex = 0;
        Complex[] complexArray = new Complex[numOfComplex]; // Need to initialize the array
        try {   
            Scanner sc = new Scanner(new File(fileName));
            String firstLine = sc.nextLine();
            firstLine = firstLine.trim();
            numOfComplex = Integer.parseInt(firstLine);
            complexArray = new Complex[numOfComplex];
            for (int i = 0; i < numOfComplex; i++) {
                String nextLine = sc.nextLine();
                nextLine = nextLine.trim();
                complexArray[i] = parseComplex(nextLine);
                }
            return complexArray;
        } 
        catch(Exception e) {
            System.out.println("Exception was thrown"); // try adding this to see if an exception is thrown.
        }
        return complexArray;
    } //<<<=== scope of `complexArray` ends here

您需要通过创建新的Complex数组来初始化complexArray对象。这是你的问题。

我认为这可行。如果一切顺利，它应该进入try子句。如果不是，它将返回大小为0的complexArray。我假设如果发生这种情况，文件有问题，这意味着你需要手动做一些事情？

Java：局部变量范围

4 个答案: