第一题
public class MyClass{
private int num ;
public void method(){
System.out.prinltn(num);
}
}
public class Test{
public static void main(String[] args){
MyClass c = new MyClass();
c.method();

}
}

运行为0

第二题
public class Fu{
private(私有) int num = 10;
}
public class Zi extends Fu{
private int num = 20;

public void method(){
System.out.println(super.num);
}
}
public class Test{
public static void main(String[] args){
Zi zi = new Zi();
zi.method();
}
}

编译报错,因为父类属性为私有变量,私有变量只有本类成员可以访问

第三题
public class Fu{
public void method(){
System.out.println("fu");
}
}
public class Zi extends Fu{

public void method(){
System.out.println("Zi");
}
}
public class Test{
public static void main(String[] args){
Fu fz = new Zi();
fz.method();
}
}

运行结果为zi, 多态创建对象,子类重写父类方法.

第四题
public class Fu{
public void method(){
System.out.println("fu");
}
}
public class Zi extends Fu{

public void method2(){
System.out.println("Zi");
}
}
public class Test{
public static void main(String[] args){
Fu fz = new Zi();
fz.method2();
}
}

编译报错,多态创建对象后,不能访问子类特有方法,必须重写父类已有方法,才可以i使用子类方法.

第五题
public class Person{
private String name;
private int age;
public Person(String name,int age){
this.name = name;
this.age = age;
}
}
public class Student extends Person{

}
public class Test{
public static void main(String[] args){
Student s = null;
System.out.println(s);
}
}

编译报错,子类继承父类,子类调用默认的Super而父类没有空参构造.

第六题
public class Test{
public static void main(String[] args){
Calendar c = new Calendar();
//假设当前系统时间为 2020年11月8日
int year = c.get(Calendar.YEAR);
System.out.println(year);
}
}