java中类的继承和访问控制

类的继承

TestPerson.java

class Person {
    private String name;
    private int age;
    public void setName(String name) {
    	this.name=name;
    }
    public void setAge(int age) {
    	this.age=age;
    }
    public String getName(){
    	return name;
    }
    public int getAge(){
    	return age;
    }
}

class Student extends Person {
    private String school;
    public String getSchool() {
    	return school;
    }
    public void setSchool(String school) {
    	this.school =school;
    } 
}

public class TestPerson {
    public static void main(String arg[]){
        Student student = new Student();
        student.setName("John");
        student.setAge(18);
        student.setSchool("SCH");
        System.out.println(student.getName());//John
        System.out.println(student.getAge());//18
        System.out.println(student.getSchool());//SCH
    }
}

 访问控制修饰符private protected public

TestAccess.java

//对于class的权限修饰只可以用public和default
public class TestAccess {
}

//权限控制
class T {
	//修饰符修饰成员变量
	private int i = 0;//private	类内部
	int j = 0;//default	类内部	同一包
	protected int k = 0;//protected	类内部	同一包	子类
	public int m = 0;//public	类内部	同一包	子类	任何地方
	
	public void m() {
		i = 9;
	}
}

class TT {
	public void m() {
		T t = new T();
		//System.out.println(t.i);//TestAccess.java:18: 错误: i可以在T中访问private，不能访问private
		System.out.println(t.j);//编译通过
	}
}