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;
    }
}

 

//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;
}