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());
//
}
}