Java面试题总结之Java基础(三)

try{

throw new ExampleB(“b”)；

}catch（ExampleA e）{

System.out.printfln（“ExampleA”）；

}catch（Exception e）{

System.out.printfln（“Exception”）；

}

import java.util.ArrayList;

import java.util.Collections;

import java.util.Iterator;

import java.util.List;

import java.util.Random;

 

public class RandomSort {

      public static void printRandomBySort() {

             Random random = new Random(); // 创建随机数生成器

             List<Integer> list = new ArrayList<Integer>();

             // 生成10 个随机数，并放在集合list 中

             for (int i = 0; i < 10; i++) {

                    list.add(random.nextInt(1000));

             }

             Collections.sort(list); // 对集合中的元素进行排序

             //第一种输出方法

             Iterator<Integer> it = list.iterator();

             int count = 0;

             while (it.hasNext()) { // 顺序输出排序后集合中的元素

                    System.out.println(++count + ": " + it.next());

             }

             //第二种输出方法

             for (Integer integer : list) {

                    System.out.println(integer);

             }

      }

 

      public static void main(String[] args) {

             printRandomBySort();

      }

}

public class ChooseSort {

   private int[] array;

   private int length;

 

   public ChooseSort(int[] array) {

      this.array = array;

      this.length = array.length;

   }

 

   /**

    * 打印数组中的所有元素

    */

   public void display() {

      for (int i : array) {

        System.out.print(i + " ");

      }

      System.out.println();

   }

 

   /**

    * 选择排序算法

    */

   public void chooseSort() {

      for (int i = 0; i < length - 1; i++) {// 做第i趟排序

        int minIndex = i;

        for (int j = minIndex + 1; j < length; j++) {// 选最小的记录

           if (array[minIndex]>array[j]) {

              minIndex = j;// 记下目前找到的最小值所在的位置

           }

        }

        // 在内层循环结束，也就是找到本轮循环的最小的数以后，再进行交换

        if (i != minIndex) { // 交换a[i]和a[minIndex]

           int temp = array[i];

           array[i] = array[minIndex];

           array[minIndex] = temp;

        }

      }

   }

 

   public static void main(String[] args) {

      int[] array = { 100, 45, 36, 21, 17, 13, 7 };

      ChooseSort cs = new ChooseSort(array);

      System.out.println("排序前的数据为：");

      cs.display();

      cs.chooseSort();

      System.out.println("排序后的数据为：");

      cs.display();

   }

}

public class TestThread {

   private int j;

 

   public TestThread(int j) {

      this.j = j;

   }

 
//增加j
   private synchronized void inc() {

      j++;

      System.out.println(j + "--Inc--" + Thread.currentThread().getName());

   }

 //减少j

   private synchronized void dec() {

      j--;

      System.out.println(j + "--Dec--" + Thread.currentThread().getName());

   }

 

   public void run() {

      new Dec().start();

      new Thread(new Inc()).start();

      new Dec().start();

      new Thread(new Inc()).start();

   }

 

   class Dec extends Thread {

      public void run() {

        for (int i = 0; i < 100; i++) {

           dec();

        }

      }

   }

 

   class Inc implements Runnable {

      public void run() {

        for (int i = 0; i < 100; i++) {

 

           inc();

        }

      }

   }

 

   public static void main(String[] args) {

      new TestThread(5).run();

   }

}

File file = new File("e:");

      File[] files = file.listFiles();

      for (int i = 0; i < files.length; i++) {

        if (files[i].isFile())

           System.out.println(files[i]);

}

File file = new File("e:\\");

      File[] files = file.listFiles();

      for (int i = 0; i < files.length; i++) {

        if (files[i].isDirectory())

           System.out.println(files[i]);

  }

System.out.println(new File("d:\\t.txt").exists());

public class Test {

   public static void main(String[] args) throws IOException {

      // 读文件:

      FileInputStream fin = new FileInputStream("e:\\tt.txt");

      byte[] bs = new byte[100];

      while (true) {

        int len = fin.read(bs);

        if (len <= 0)

           break;

        System.out.print(new String(bs, 0, len));

      }

      fin.close();

      // 写文件:

      FileWriter fw = new FileWriter("e:\\test.txt");

      //System.getProperty("line.separator")相当于"/n"\n’ 这样写的话，剔除了平台无关性

      fw.write("hello world!" + System.getProperty("line.separator"));

      fw.write("你好！郑州！");

      fw.close();

 

   }

 

}

public static int countWords(String file, String find) throws Exception {

      int count = 0;

      Reader in = new FileReader(file);

      int c;

      while ((c = in.read()) != -1) {

        while (c == find.charAt(0)) {

           for (int i = 1; i < find.length(); i++) {

              c = in.read();

              if (c != find.charAt(i))

                 break;

              if (i == find.length() - 1)

                 count++;

           }

        }

      }

      return count;

}

import java.net.*;

import java.io.*;

 

public class Server {

   private ServerSocket ss;

   private Socket socket;

   private BufferedReader in;

   private PrintWriter out;

 

   public Server() {

      try {

        //创建 ServerSocket 对象（并绑定端口）

        ss = new ServerSocket(10000);

        while (true) {

           //调用 accept 方法，等待来自客户端的连接

           socket = ss.accept();

           String RemoteIP = socket.getInetAddress().getHostAddress();

           String RemotePort = ":" + socket.getLocalPort();

           System.out.println("A client come in!IP:" + RemoteIP + RemotePort);

           //调用 getXXXStream 方法，进行 I/O操作

           in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

           String line = in.readLine();

           System.out.println("Cleint send is :" + line);

           out = new PrintWriter(socket.getOutputStream(), true);

           out.println("Your Message Received!");

           out.close();

           in.close();

           //关闭 Socket

           socket.close();

        }

      } catch (IOException e) {

        out.println("wrong");

      }

   }

 

   public static void main(String[] args) {

      new Server();

   }

}

import java.io.*;

import java.net.*;

 

public class Client {

   Socket socket;

   BufferedReader in;

   PrintWriter out;

 

   public Client() {

      try {

        System.out.println("Try to Connect to 127.0.0.1:10000");

        //1.创建 Socket 对象，并连接服务器 （ip字符串,端口号）

        socket = new Socket("127.0.0.1", 10000);

        System.out.println("The Server Connected!");

        System.out.println("Please enter some Character:");

        BufferedReader line = new BufferedReader(new InputStreamReader(System.in));

        out = new PrintWriter(socket.getOutputStream(), true);

        out.println(line.readLine());

        //2.调用 getXXXStream 方法，进行 I/O操作

        in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

        System.out.println(in.readLine());

        out.close();

        in.close();

        //3、关闭 Socket

        socket.close();

      } catch (IOException e) {

        out.println("Wrong");

      }

   }

 

   public static void main(String[] args) {

      new Client();

   }

}