在线等 孙鑫程序出现的问题

[shunzyt]

我在孙鑫老师的视频里看到他的例子代码，然后我自己默写修改，最后出现3个问题，我不知道为什么，代码如下，希望高手编译一下，看下为什么，告诉我下，不胜感激，我想了好久没想明白
public class Student implements Cloneable
{
int age;
String name;
Professor p;
Student(int age,String name,Professor p)
{
this.name=name;
this.age=age;
this.p=p;
}
public Object clone()
{ Object o=null;
try
{
o=super.clone();
}
catch(CloneNotSupportedException e)
{
System.out.println(e.toString());
}
return o;
}
}
class Professor implements Cloneable
{
int age;
String name;
Professor(int age,String name)
{
this.name=name;
this.age=age;
}
public Object clone()
{ Object o=null;
try
{
o=super.clone();
}
catch(Exception e)
{
System.out.println(e.toString());
}
return o;
}
}
class Test
{
Professor p=new Professor(44,"ccc");
Student s1=new Student(22,"aaa",p);
public static void main(String[] args)
{
System.out.println(s1.p.name);
}
}

[dracularking]

public class Test {
	public static void main(String[] args) {
		Professor p = new Professor(44, "ccc");
		Student s1 = new Student(22, "aaa", p);
		System.out.println(s1.p.name);
	}
}

有main方法的类才能是public的
还有p,s1得是static的引用型 如果在main中使用

[不更新了 不更新了在这里]

1楼正解
class Test
{
Professor p=new Professor(44,"ccc");
Student s1=new Student(22,"aaa",p);
public static void main(String[] args)
{
System.out.println(s1.p.name);
}
}

这样写是不行的,因为无法从静态上下文中引用非静态 变量 s1,p

main方法是静态方法,
所以要改成:

class Test
{
public static void main(String[] args)
{
Professor p = new Professor(44, "ccc");
Student s1 = new Student(22, "aaa", p);
System.out.println(s1.p.name);
}
}
还有如果你是在dos下编译运行,那么应该是:
javac Student.java
java Test

[ltc_mouse]

1楼提到“有main方法的类才能是public的”
这个似乎不正确吧

通常，main方法只是提供了一个如何使用一个或多个Java类的例子，不是必需的
2楼指出的在dos下编译运行，需要使用不同参数，就是因为Student类中没有main方法，main方法是放在Test类中的（这种做法是有好处的，将来打包程序时，不用改源代码，直接删除Test.class就可以了）

[Awing911]

package cn.edu.csu;

public class Test1 {

public static void main(String args[]){

Professor p = new Professor(44, "ccc");
Student s1 = new Student(22, "aaa", p);
System.out.println(s1.p.name);
}

}

结果:
ccc

[leem06]

import java.sql.Connection;
import java.sql.DriverManager;

class Student implements Cloneable {
	int age;

	String name;

	Professor p;

	Student(int age, String name, Professor p) {
		this.name = name;
		this.age = age;
		this.p = p;
	}

	public Object clone() {
		Object o = null;
		try {
			o = super.clone();
		} catch (CloneNotSupportedException e) {
			System.out.println(e.toString());
		}
		return o;
	}
}

class Professor implements Cloneable {
	int age;

	String name;

	Professor(int age, String name) {
		this.name = name;
		this.age = age;
	}

	public Object clone() {
		Object o = null;
		try {
			o = super.clone();
		} catch (Exception e) {
			System.out.println(e.toString());
		}
		return o;
	}
}

public class Test {
	public static void main(String[] args) {
		Professor p = new Professor(44, "ccc");

		Student s1 = new Student(22, "aaa", p);
		System.out.println(s1.p.name);
	}
}