Scanner 和 BufferedReader 的 try、catch 和 finally 的正确方法

Question

试图了解在我的主要方法中对 Scanner 和 BufferedReader 进行 try-catch-finally 的最佳和最有效的方法。应该有两个不同的捕获物还是将它们合并为一个？

    public static void main(String[] args) throws IOException {
    //open file input stream
    try {
        BufferedReader reader = new BufferedReader(new FileReader("DATABASE.txt"));

        //read file line by line
        String line = null;
        Scanner scan = null;

        BST tree = new BST();
        line = reader.readLine();

        while(line != null) {
            Employee emp = new Employee();
            scan = new Scanner(line);
            scan.useDelimiter(",");

            while(scan.hasNext()){
                emp.setEmployeeID(Integer.parseInt(scan.next()));
                emp.setFirstName(scan.next());
                emp.setLastName(scan.next());
                emp.setSalary(Double.parseDouble(scan.next()));
                line = reader.readLine();
            }
            tree.insert(emp);
        }
        reader.close();
        tree.inOrder();
        //System.out.println(empList);
    } catch(IOException e){
        e.printStackTrace();
    }

Answer 1

单个 catch 块应该足够了。您可以添加一个 finally 块来关闭 reader 和扫描仪实例（如果它们不为空）。这样，无论 try 块是否正常完成或抛出异常，它们都将被关闭。应该添加空检查，因为 try 块可能无法到达两个对象的初始化，因为可能会发生异常。

Answer 2

在 try-catch-finally 代码块外声明了 Scanner scan = null 和 BufferedReader reader = null; 并在 try 块内初始化了它们。异常被捕获，他们都到达了 finally 块。

public static void main(String[] args) throws IOException {
    Scanner scan = null;
    BufferedReader reader = null;
    //open file input stream
    try {
        reader = new BufferedReader(new FileReader("DATABASE.txt"));

        //read file line by line
        String line = null;
        Scanner scan = null;

        BST tree = new BST();
        line = reader.readLine();
        scan = new Scanner(line);
        while (line != null) {
            Employee emp = new Employee();
            scan.useDelimiter(",");

            while (scan.hasNext()) {
                emp.setEmployeeID(Integer.parseInt(scan.next()));
                emp.setFirstName(scan.next());
                emp.setLastName(scan.next());
                emp.setSalary(Double.parseDouble(scan.next()));
                line = reader.readLine();
            }
            tree.insert(emp);
        }
    }catch (IOException e) {
        e.printStackTrace();
    } finally {
        reader.close();
        scan.close();
    }
}

Answer 3

您不需要同时使用 BufferedReader 和 Scanner。一个Scanner就够了：

public static BST readFile(File file) throws FileNotFoundException {
    try (Scanner scan = new Scanner(file)) {
        scan.useLocale(Locale.US);  // mandatory for read double values

        BST bst = new BST();

        while (scan.hasNext()) {
            Employee employee = new Employee();
            employee.setEmployeeID(scan.nextInt());
            employee.setFirstName(scan.next());
            employee.setLastName(scan.next());
            employee.setSalary(scan.nextDouble());
            bst.insert(employee);
        }

        bst.inOrder();
        return bst;
    }
}

Scanner 和 BufferedReader 的 try、catch 和 finally 的正确方法

Proper method for a try, catch, and finally for Scanner and BufferedReader

java

try-catch

ioexception