JavaSE coding questions strengthening exercises 6

1. Write the code for selection sort, sort the array to an int

public class TestSelectSort {
  public static void main(String[] args) {
    int [] arr = {87,65,5,5,43,21};
    System.out.print("排序前：[ ");
    for (int i : arr){
      System.out.print(i+" ");
    }
    System.out.println("]");
    selectSort(arr);
    System.out.print("排序后：[ ");
    for (int i : arr){
      System.out.print(i+" ");
    }
    System.out.println("]");
  }
  public static void selectSort(int[] arr){
    for (int i = 0;i < arr.length - 1;i++){
      int minIndex = i;
      for (int j = i;j < arr.length - 1;j++){
        if (arr[minIndex] > arr[j + 1]){
          minIndex = j + 1;
        }
      }
      if (minIndex != i){
        int temp = arr[minIndex];
        arr[minIndex] = arr[i];
        arr[i] = temp;
      }
    }
  }
}

operation result:

 

 2. the contents of the text file exam.txt IO read class E package tray, each read line of text in each input line as a generic collection ArrayList contents into the collection and use of reinforcing outputs for display.

public  class TestReader {
   public  static  void main (String [] args) { 
    String path = "E: /exam.txt" ; 
    outputMethod (path); 
  } 

  Private  static  void outputMethod (String path) {
     / ** 
     * Create collection object 
     * / 
    List <String> List = new new the ArrayList <String> ();
     / ** 
     * Create Object buffer 
     * / 
    the BufferedReader br = null ;
     the try { 
      br = new new the BufferedReader ( new new FileReader(path));
      /**
       * 读取数据每次读取一行
       */
      String line = br.readLine();
      while (line != null){
        list.add(line);
        line = br.readLine();
      }
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }finally {
      try {
        if (br != null){
          br.close();
        }
      } catch (IOException e) {
        e.printStackTrace();
      }
      for (String s : list){
        System.out.println(s);
      }
    }
  }
}

Text:

 

Result of the program:

 

 Note: To save the text in UTF-8 format, or else the program will be reported garbled reading, as shown below (saved in ANSI text format):

 

 3. Write two threads, one thread print integer of 1-52, another thread printing letters AZ. Print order 12A34B56C ... .5152Z. That is, after the order from small to large integers and letters printed, and printing each of two integers, a printed letter, alternating cycles print until the end of the letter Z and the integer 52.

/**
 * 打印类
 */
public class Printer {
  /**
   * 设为1，方便计算3的倍数
   */
  private int index = 1;

  /**
   * 打印数字的方法，每打印两个数字，等待打印一个字母
   */
  public synchronized void print(int i){
    while (index % 3 == 0){
      try {
        wait();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
    System.out.print(""+i);
    index++;
    notifyAll();
  }
  /**
   * 打印字母，每打印一个字母等待打印两个数字
   */
  public synchronized void print(char c){
    while (index % 3 != 0){
      try {
        wait();
      } catch (InterruptedException e) {
        e.printStackTrace();
      }
    }
    System.out.print(""+c);
    index++;
    notifyAll();
  }
}

/**
 * 打印数字线程
 */
public class NumberPrinter extends Thread {
  private Printer p;

  public NumberPrinter(Printer p) {
    this.p = p;
  }

  public void run() {
    for (int i =1;i <= 52;i++){
      p.print(i);
    }
  }
}

/**
 * 打印字母线程
 */
public class LetterPrinter extends Thread {
  private Printer p;
  public LetterPrinter(Printer p){
    this.p = p;
  }
  public void run(){
    for (char c = 'A';c <= 'Z';c++){
      p.print(c);
    }
  }
}

public class TestThread {
  public static void main(String[] args) {
    /**
     * 创建打印机对象
     */
    Printer p = new Printer();
    /**
     * 创建线程对象并启动线程
     */
    Thread t1 = new NumberPrinter(p);
    Thread t2 = new LetterPrinter(p);
    t1.start();
    t2.start();
  }
}

运行结果：