day13 面向对象练习

//1

 public class Area_interface
 {
     public static void main(String[] args)
     {
         Rect r = new Rect(15, 12);
         Circle c = new Circle(8);
         System.out.println(r.getArea());
         System.out.println(c.getArea());
     }
 }
 
 interface Areable{
     double getArea();
 }
 
 class NotValueException extends RuntimeException{
     NotValueException(String message){
         super(message);
     }
 }
 
 // 矩形
 class Rect implements Areable{
     private int length,width;
     public Rect(int length,int width) {
         if (length <= 0 || width <= 0){
             throw new NotValueException("数值非法!");
         }
         this.length = length;
         this.width = width;
     }
     public double getArea()
     {
         return length*width;
     }
 }
 
 // 圆形
 class Circle implements Areable{
     private int radius;
     private static final double PI = 3.14;
     public Circle(int radius) {
         this.radius = radius;
     }
     public double getArea()
     {
         return PI*radius*radius;
     }
 }

//2

 public int search_char(char[] chs, char key)
 {
     if(chs==null){
         throw new IllegalArgumentException("数组为空");
     }
     for(int x = 0;x < chs.length;x++){
         if(key==chs[x]){
             return x;
         }
     }
     return -1;
 }

//3

 //first method
 int max = 0;     //初始化为数组中的任意一个角标
 for(int  x = 1; x < cir.length; x++){
     if(cir[x].radius > cir[max].radius){
         max = x;
     }
 }
 return  cir[max].radius;
 
 //second
 double max = cir[0].radius;    //初始化为数组任意一个元素的半径
 for(int  x = 1; x < cir.length; x++){
     if(cir[x].radius >max){
         max = cir[x].radius;
     }
 }
 return max;

//4

 class Person{
     private int age;
     private String name;
     public Person(int age, String name) {
         super();
         this.age = age;
         this.name = name;
     }
 
     public void say()
     {
         System.out.println(name+"  "+age);
     }
     //下面两个都是通过右键搞定的
     //get和set方法
     public int getAge()
     {
         return age;
     }
     public void setAge(int age)
     {
         this.age = age;
     }
     public String getName()
     {
         return name;
     }
     public void setName(String name)
     {
         this.name = name;
     }
     //hashcode和equals方法
     @Override
     public int hashCode()
     {
         final int prime = 31;
         int result = 1;
         result = prime * result + age;
         result = prime * result + ((name == null) ? 0 : name.hashCode());
         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;
         return true;
     }
 }

equals方法通过eclipse自动生成

//5

 public boolean equals(Object other){
     if( !(other  instanceof  Circle) ){
         throw new ClassCastException(other.getClass().getName+"类型错误");
     }
     Circle c = (Circle)other;
     return  c.radius==this.radius;
 }