java新手笔记18 类比较

1、Shap类

package com.yfs.javase;



public class Shape /*extends Object */{  //默认继承object  object方法全部继承

	//计算面积方法

	public double getArea() {

		System.out.println("计算面积");

		return 0;

	}



}

 2.Circle类

package com.yfs.javase;



public class Circle extends Shape {

	

	private double r;

	

	public Circle(double r) {

		this.r = r;

		System.out.println("创建圆形面积");

	}

	

	public double getArea() {//覆盖父类的方法

		System.out.println("计算圆形面积...");

		return 3.14 * r * r;

	}



}

 3.Rangton类

package com.yfs.javase;



public class Rangton  extends Shape {

	

	private double width;

	private double length;

	

	public Rangton(double width, double length) {

		this.width = width;

		this.length = length;

		System.out.println("创建矩形面积");

	}

	

	public double getArea() {

		System.out.println("计算矩形面积...");

		return width * length;

	}



}

 4.Trantangel类

package com.yfs.javase;



public class Trantangle  extends Shape {

	

	private double height;

	private double width;

	

	public Trantangle(double height, double width) {

		this.height = height;

		this.width = width;

		System.out.println("创建三角形面积");

	}

	

	public double getArea() {

		System.out.println("计算三角形面积...");

		return 1.0 / 2 * width * height;

	}





}

 5.Shap 测试

package com.yfs.javase;



import java.util.Date;

import java.util.Random;

import java.util.Scanner;



public class Demo1 {



	/**

	 * @param args

	 */

	public static void main(String[] args) {

		Shape shape = new Shape();

		shape.getClass();

		



		Object obj = new Object();// 所有对象的基类

		// 方法

		boolean isTrue = obj.equals(shape);

		System.out.println(isTrue);

		obj.getClass();

		obj.hashCode();

		obj.toString();

		//obj.notify();

		

		obj = shape;

		

		obj = new Random();

		

		obj = new Scanner(System.in);

		

		Circle c = new Circle(2);

		

		obj = c;

		shape = c;

		

		obj = shape;

		//继承object

		c.getClass();

		

		method(shape);

		

		//method(new Date());



	}

	

	public static void method(Object obj) {

		//obj.getArea();

		Shape s = (Shape)obj;

		s.getArea();

	}



}

 6.Person 类(自定义比较）

package com.yfs.javase;



public class Person {



	private String name;

	private char sex;

	private int age;



	public Person() {



	}



	public Person(String name, char sex, int age) {

		this.name = name;

		this.sex = sex;

		this.age = age;

	}



	@Override

	public String toString() {

		return "Person [name=" + name + ", sex=" + sex + ", age=" + age + "]";

	}



	public String getName() {

		return name;

	}



	public void setName(String name) {

		this.name = name;

	}



	public char getSex() {

		return sex;

	}



	public void setSex(char sex) {

		this.sex = sex;

	}



	public int getAge() {

		return age;

	}



	public void setAge(int age) {

		this.age = age;

	}



	public void sayHello() {

		System.out.println(name + " Hello ....");

	}



	@Override

	public int hashCode() {

		final int prime = 31;

		int result = 1;

		result = prime * result + age;

		result = prime * result + ((name == null) ? 0 : name.hashCode());

		result = prime * result + sex;

		return result;

	}



	@Override

	public boolean equals(Object obj) {

		if (this == obj)

			return true;

		if (obj == null)

			return false;

		if (getClass() != obj.getClass())

			return false;

		Person other = (Person) obj;

		if (age != other.age)

			return false;

		if (name == null) {

			if (other.name != null)

				return false;

		} else if (!name.equals(other.name))

			return false;

		if (sex != other.sex)

			return false;

		return true;

	}

	



//	@Override

//	public int hashCode() {

//		return 123;

//	}

//

//	@Override //自定义类 覆盖equals方法 自己定义对象比较规则

//	public boolean equals(Object obj) {

//		Person other = (Person)obj;

//		return this.name.equals(other.name) && sex == other.sex && age == other.age;

//	}

}

 7.Person测试

package com.yfs.javase;



public class Demo2 {



	/**

	 * @param args

	 */

	public static void main(String[] args) {

		Person p1 = new Person();

		System.out.println("p1.hashCode() : " + p1.hashCode());

		

		Person p2 = new Person();//hashCode对象的散列码

		System.out.println("p2.hashCode() : " + p2.hashCode());

		

		Person p3 = new Person();

		System.out.println("p3.hashCode() : " + p3.hashCode());

		

		p1.sayHello();

		p2.sayHello();

		p3.sayHello();

		

		System.out.println("p1 == p2 ? " + (p1 == p2));



	}



}

 8.Person类

package com.yfs.javase;



public class Demo3 {



	/**

	 * @param args

	 */

	public static void main(String[] args) {

		Person p1 = new Person("张三",'男',20);

		

		Person p2 = new Person("张三",'男',20);

		

		System.out.println("p1 == p2 : " + (p1 == p2));

		

		//比较对象中属性只是否相等

		System.out.println(p1.getAge() == p2.getAge());

		System.out.println("==  " + (p1.getName() == p2.getName()));

		System.out.println("equals : " + p1.getName().equals(p2.getName()));

		System.out.println("p1.equals(p2) : " + p1.equals(p2));

		System.out.println("======================");

		System.out.println("p1.hashcode :" + p1.hashCode());

//		String s1 = new String("abc");

//		String s2 = new String("abc");

//		System.out.println("s1 == s2 : " + (s1 == s2));

//		System.out.println("s1.equals(s2) : " + s1.equals(s2));//String 类覆盖equals方法

		

		Object obj = p1;

		System.out.println(obj.getClass().getName());

//		



	}



}