Java1-赵贺1407084127

[Diamond-Dogs]

1. 删羊

import java.util.ArrayList;
public class S111 {
    public static void main(String[] args) {
        int[] a=new int[]{1,2,3,4,5};
        Sheep[] sheep=new Sheep[]{
                new Sheep("喜羊羊"),new Sheep("美羊羊"),new Sheep("暖洋洋"),
                new Sheep("沸羊羊"),new Sheep("懒洋洋")};
                System.out.println(sheep[2].getName());
        ArrayList<Sheep> sheepList=new ArrayList();
        sheepList.add(new Sheep("喜羊羊"));
        sheepList.add(new Sheep("美羊羊"));
        sheepList.add(new Sheep("暖洋洋"));
        sheepList.add(new Sheep("沸羊羊"));
        sheepList.add(new Sheep("懒洋洋"));

方法一

        int k=sheepList.size();
          for(int i=k-3;i<k;i++)
        {
            sheepList.remove(k-3);
        }

方法二

        for(int i=0;i<3;i++)
        {
            sheepList.remove(sheepList.size()-1);
        }

方法三

        for (int j=2;j<sheepList.size();j--)
        {
            sheepList.remove(j);
            j++;
        }
        for(int i=0;i<sheepList.size();i++){
            System.out.println(((Sheep)(sheepList.get(i))).getName());
        }
        }
        }

迭代器

        int j=0;
        Iterator it = sheepList.iterator();
        for(;it.hasNext();){
             if(j>1)
            {
                 sheepList.remove(j);
             }
             else{
                 it.next(); 
                    j++;
             }
         }

2. 批量写入文件

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import javax.swing.plaf.synth.SynthSeparatorUI;

public class FlieTest {
public static void main(String[] args){
    File manyfile=new File("D://test1");
    File file;
OutputStream os=null;
try{
    if(!manyfile.exists()){
        manyfile.mkdir();
    }
   for(int i=0;i<=10;i++){
       file=new File(manyfile,"helloworld"+i+".txt");
       os=new FileOutputStream(file);
       String s="中北大学安卓实验室";
       os.write(s.getBytes());
   }  
   }catch(FileNotFoundException e) {
   e.printStackTrace();
   }catch(NumberFormatException e) {
   e.printStackTrace();
   }catch (IOException e) {
   e.printStackTrace();
   }
   }
   }

3. Thread和Runnable区别

 public static void main(String args[]) {
 Thread1 s1=new Thread1();  //Thread对象s1只能开启一个线程
 Thread1 s2=new Thread1();  //Thread对象s2只能开启一个线程
 s1.start();  
 s2.start(); 
 Thread2 t1=new Thread2();  
 Thread ta=new Thread(t1,"A");  
 Thread tb=new Thread(t1,"B");  //使用Runnable接口创建的接口使用同一个对象t1
 ta.start();  
 tb.start(); 
 }

  public class Thread1 extends Thread{
    public void run(){  
      for(int i=0;i<5;i++){  
    System.out.println(Thread.currentThread().getName()+" "+i);    
        }  
 } 
 }
  public class Thread2 implements Runnable{
    public void run() {   
    {  
        for(int i=0;i<5;i++)  
        {  
            System.out.println(Thread.currentThread().getName()  
                    +" "+i);  
        }
 }
 }
 }

一个Thread对象只能开启一个线程,而一个实现了Runnable接口的对象可以开启多个线程
java是单继承的，使用Runnable