![](https://lstatic.shangxueba.com/jiandati/h5/images/m_q_title.png)
阅读下面代码: import java.util.ArrayList; public class Demo { public static void main(String[] args) { ArrayList list = new ArrayList(); list.add("aaa"); list.add("bbb"); list.add("ccc"); for (Object obj :
A.[aaa,ccc]
B.[aaa,bbb,ccc]
C.[ ]
D.以上都不对
A.[aaa,ccc]
B.[aaa,bbb,ccc]
C.[ ]
D.以上都不对
import Java.util.ArrayList;
import java.util.List;
(1) class AbstractFile{
protected String name;
public void printName(){System.out.println(name);}
public abstract boolean addChild(AbstractFile file);
public abstract boolean removeChild(AbstractF ile file);
public abstract List getChildren();
}
class File extends AbstractFile{
public File(String name){this.name=name;}
public boolean addChild(AbstractFile file){return false;}
public boolean removeChild(AbstractFile file){return false;}
public List getChildren(){return (2) ;}
}
class Folder extends AbstractFile{
private List childList;
public Folder(String name){
this.name=name;
this.childList=new ArrayList();
}
public boolean addChild(AbstractFile file) { return childList.add(file);}
public boolean removeChild(AbstractFile file){return childList.remove(file);}
public (3) getChildren(){return (4) ;}
}
public class Client{
public static void main(String[] args){
//构造一个树形的文件/目录结构
AbstractFile rootFolder= new Folder("c:\\ ");
AbstractFile compositeFolder=new Folder("composite");
AbstractFile windowsFolder=new Folder("windows");
AbstractFile file=new File("TestComposite.java");
rootFolder.addChild(compositeFolder) ;
rootFolder.addChild(windowsFolder);
compositeFolder.addChild(file) ;
//打印目录文件树
printTree(rootFolder);
}
private static void printTree(AbslractFile ifile){
ifile.printName();
List children=ifile.getChildreno:
if(children==null) return;
for (AbstractFile file:children) {
(5) ;
}
}
}
该程序运行后输出结果为:
c:\
composite
TestComposite.java
Windows
import java.awt.*;
public class Exam11_1
{
private Frame. f;
private Button b1,b2,b3,b4;
public static void main(String args[]
{
Exam11_1 that = new Exam11 1 ();
that.go();
}
public void go()
{
______;
f.setLayout(new FlowLayout()) ;;
b1 = new Button ("Button 1");
b2 = new Button ("Button 2");
b3 = new Button ("Button 3");
b4 = new Button ("Button 4");
f.add (b1);
f.add (b2);
f.add (b3);
f.add (b4);
f.pack ();
f.setVisible (true);
}
}
请在程序中画线处填写正确的语句【 】,以便编译运行程序后得到正确的结果。
以下程序实现读写文件的功能,请把_________上的语句填写完整。 import java.io.*; public class ioTest { public static void main(String args[]) { //首先,基于字节输出流FileOutputStream向文件中写入数据 try { FileOutputStream fout= new FileOutputStream(new File("d:/my.txt")); fout.write("2017122108 男 王晓飞 计算机计171 江苏苏州".getBytes()); fout.close(); //关闭输出流 } catch(IOException e) { } //接下来,基于字节输入流FileInputStream,将文件中的信息读出并显示 try { FileInputStream fin=new FileInputStream(new File("d:/my.txt")); byte[] data=new byte[200];//接收从文件中读到的数据 int n;//n为实际读到的字节数 while((n=fin.read(__________))!=-1) { String s=new String(data,0,n);//将读到的数据拼成字符串 System.out.println(s);//输出 } } catch(IOException ex) { } } }
A、FileInputStream data=new FileInputStream(new File ("d:\\data.txt"));
B、FileInputStream data=new FileInputStream("d:\\data.txt");
C、BufferedOutputStream bo=new BufferedOutputStream("d:\\data.txt");
D、BufferedOutputStream bo=new BufferedOutputStream(new FileOutputStream("d:\\da.txt"));
B.编译成功,运行失败,运行时会抛出NullPointerException
C.编译成功,运行成功,运行结果是: [hello,null]
D.编译成功,运行成功,运行结果是: [hello, hello, null]
B、ByteArrayOutputStream
C、BufferedOutputStream
D、FileWriter
A、compareTo(Object obj)
B、boolean remove(Object obj)
C、boolean constainsAll(Collection c)
D、int size()
A、Vector 在Java的第一个版本就引入了,也就是说vector是一个合法规范的类
B、ArrayList在Java1.2版本引入的,是Java 集合框架的组成部分
C、Vector是同步的
D、ArrayList是不同步的
A、size
B、length
C、dimension
D、count
为了保护您的账号安全,请在“简答题”公众号进行验证,点击“官网服务”-“账号验证”后输入验证码“”完成验证,验证成功后方可继续查看答案!