java新手笔记17 参数

package com.yfs.javase;

public class ParamDemo {

	public static void main(String[] args) {
		int a = 3, b = 5;
		change(a,b);
		System.out.println("a = " + a  + "  b = " + b);

		Point p = new Point();
		p.x = 10;
		p.y = 20;
		change(p);

		System.out.println("p.x = " + p.x  + "  p.y = " + p.y);

	}

	public static void change(Point p) {//引用指向  是对象
		int c = p.x;
		p.x = p.y;
		p.y = c;

	}

	public static  void change(int a, int b) {//局部变量  传入是数值
		System.out.println("================");
		System.out.println("||||||  a = " + a  + "  b = " + b +"||||||");

		int c = a;
		a = b;
		b = c;
		System.out.println("||||||  a = " + a  + "  b = " + b +"||||||");
		System.out.println("================");
	}

}

class Point {
	int x;
	int y;
}

1.Person

package com.yfs.javase;

public class Person {

	public Person() {
		System.out.println("javase.Person  ***");
	}
}

2. other Person

package com.yfs.javase.other;

public class Person {

	public Person() {
		System.out.println("other.Person 对象...");
	}

}

3.Person 测试

package com.yfs.javase.other;

import com.yfs.javase.Person;

public class PersonTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Person p1 = new Person();

		com.yfs.javase.other.Person p2 = new com.yfs.javase.other.Person();

	}

}

4.default

package com.yfs.javase.other;

 class DefaultDemo {

}

  class Other {

  }

  /*public*/ class Demo {

  }

5.公有类

package com.yfs.javase.other;
//一个java文件只能有一个public 修饰的类
// 类与文件同名
public /*final*/ class PublicClass {
	private String name;
	public int age;
	protected char sex;
	int score ;
	static final int id ;//= 520;//只有一份 所有对象共享
	static {
		id = 200;
	}
	public PublicClass() {
		//id = 100;
	}
	//方法的权限
	public final void publicMethod() {
		//id = 350;
	}

	private void privateMethod() {
		protectedMethod();
	}

	protected void protectedMethod() {

	}

	/*default*/ void defaultMethod() {
		protectedMethod();
	}
}

/*default  public*/ class DefaultClass {

}

6.测试

package com.yfs.javase.other;
//同一包下
public class AccessTest1 {

	public static void main(String[] args) {
		PublicClass pc = new PublicClass();
		pc.publicMethod();
		//pc.privateMethod();私有方法不能访问
		pc.protectedMethod();
		pc.defaultMethod();
	    pc.age = 20;
	    pc.score = 90;

	}

}

7.包外测试

package com.yfs.javase;

import com.yfs.javase.other.PublicClass;

//不同包下
public class AccessTest2 {

	public static void main(String[] args) {
		PublicClass pc = new PublicClass();
		pc.publicMethod();
		//pc.privateMethod();私有方法不能访问
		//pc.protectedMethod();protected方法不能访问
		//pc.defaultMethod();defautl方法不能访问

	}

}

class Child  extends PublicClass {

	public void test () {
		//privateMethod();
		protectedMethod();//子类可以访问
		//defaultMethod();//不同包不能访问
	}
//	@Override
//	public final void publicMethod() {
//		// TODO Auto-generated method stub
//
//	}
}