这行代码为什么不可以运行求支点

Question

public class lx {
class Computer {
String brand; //品牌 }
}

            public class SxtStu2 {
                // field
                int id;
                String sname;
                int age;
                Computer comp;

                void study() {
                    System.out.println("我正在学习！使用我们的电脑，" + comp.brand);
                }

                SxtStu2() {

                }

                public static void main(String[] args) {
                    SxtStu2 stu = new SxtStu2();
                    stu.sname = "张三";
                    Computer comp = new Computer();
                    comp.brand = "联想";
                    stu.comp = comp;
                    stu.study();

                }
                }
            }

Answer 1

main函数最好别写在内部类里面，因为IDE会在外部类编译出的文件中寻找main函数作为程序入口
代码最好这么写：

class lx {
    class Computer {
        String brand; // 品牌 }
    }

    public class SxtStu2 {
        // field
        int id;
        String sname;
        int age;
        Computer comp;

        void study() {
            System.out.println("我正在学习！使用我们的电脑，" + comp.brand);
        }
        SxtStu2() {
        }
    }
    public static void main(String[] args) {
        lx x = new lx();
        SxtStu2 stu = x.new SxtStu2();
        stu.sname = "张三";
        Computer comp = x.new Computer();
        comp.brand = "联想";
        stu.comp = comp;
        stu.study();
    }
}