作业

public    static void main(String []ages){
       

        List<Object> list=new ArrayList<Object>();
        
        for(int i=0;i<100;i++){
            list.add(i);
        }
        
        //System.out.println(list.get(10));
        
        Iterator<Object>it= list.iterator();
        
        //System.out.println("??");
        
        while(it.hasNext()){
            
            Object x=it.next();//for each 没有的，需要一个中间变量来转化
            
            //移除10到20
            for(int i=10;i<20;i++){
                if(x.equals(i)){
                    it.remove();
                    //System.out.println("hehe");
                }
            }
        }        
        
        System.out.println(list.get(10));
       
       

父类子类

父类

public class pikaqiu {
    
    public void zhongquan(){
        System.out.println("我的拳头十吨重");
    }
    
    public void fute(){
        System.out.println("十万伏特");
    }

    public void linghuo( int a){
        System.out.println("我灰常灵活");
    }
}

子类

public class leiqiu extends pikaqiu {
    
    public void zhongquan(){
        System.out.println("看我的百万吨重拳");
    }
    
    public void fute(){
        System.out.println("我的电压也是百万");
    };
     
    public void linghuo(){
        System.out.println("好吧我是个胖子");
    }
    
    
    //Object 强制转换
    public static Object zhuanhua(int i){
    Object zhuan    =null;
        
        if(i==1){
            zhuan=new pikaqiu();
        }
        else{
            zhuan=new leiqiu();    
        }
        return zhuan;
    }
    
    
    
    
    public static void main(String []ages){
        
        //
        leiqiu a=new leiqiu();
        
        a.fute();
        
        a.zhongquan();
        
        a.linghuo();
        
        a.linghuo(0);
        
        
        //子转父
        
        Object b=new leiqiu();
        
        pikaqiu c=(pikaqiu) b;
        
        c.zhongquan();
        
        c.fute();
        
        //父转子
        pikaqiu d=new leiqiu();
        
        d.zhongquan();
        
        
        //Object的中间转化
        pikaqiu e= (pikaqiu) leiqiu.zhuanhua(1);
        
        
        
        
        
    }

}