java常见报错及解决方案总结

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    // 缺少右大括号
}

public class Main {
    public static void main(String[] args) {
        String str = null;
        System.out.println(str.length());  // 空指针异常
    }
}

public class Main {
    public static void main(String[] args) {
        int[] arr = new int[3];
        arr[5] = 10;  // 数组下标越界
    }
}

public class Main {
    public static void main(String[] args) {
        Object obj = new String("Hello");
        Integer num = (Integer) obj;  // 类型转换异常
    }
}

import java.io.*;

public class Main {
    public static void main(String[] args) throws IOException {
        FileReader fr = new FileReader("nonexistent_file.txt");  // 文件未找到
    }
}

public class Main {
    public static void main(String[] args) {
        int result = 10 / 0;  // 除以零异常
    }
}

public class Main {
    public static void main(String[] args) {
        Thread t = new Thread(() -> System.out.println("Hello"));
        t.start();
        t.start();  // 重复启动线程
    }
}

public class Main {
    public static void main(String[] args) throws NoSuchMethodException {
        Class<?> clazz = Main.class;
        clazz.getMethod("nonExistentMethod");  // 方法未定义异常
    }
}

public class Main {
    private static final Object lock1 = new Object();
    private static final Object lock2 = new Object();

    public static void main(String[] args) {
        Thread t1 = new Thread(() -> {
            synchronized (lock1) {
                System.out.println("Thread 1 holding lock 1...");
                try { Thread.sleep(100); } catch (InterruptedException e) {}
                synchronized (lock2) {
                    System.out.println("Thread 1 holding lock 2...");
                }
            }
        });

        Thread t2 = new Thread(() -> {
            synchronized (lock2) {
                System.out.println("Thread 2 holding lock 2...");
                try { Thread.sleep(100); } catch (InterruptedException e) {}
                synchronized (lock1) {
                    System.out.println("Thread 2 holding lock 1...");
                }
            }
        });

        t1.start();
        t2.start();
    }
}

public class Main {
    public static void main(String[] args) throws ClassNotFoundException {
        Class.forName("com.example.NonExistentClass");  // 类未找到异常
    }
}