package JavaTest;

public class Test {

public static void main(String[] args) {

String s1="Hello!";

String s2="World";

String s3=s1+s2;

System.out.println(s3);

}

}

package JavaTest;

public class Test {

public static void main(String[] args) {

StringBuilder s1=new StringBuilder(" Hello! ");

StringBuilder s2=s1;

System.out.println(s2.deleteCharAt(6));

}

}

package JavaTest;

public class Test {

	public static void main(String[] args) {

		 if (args[0].equals("-h"))

			 System.out.print("Hello");

		    else if(args[0].equals("-g"))

		    	System.out.print("goodbye,");

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

		    System.out.print(" "+args[i]);

		  System.out.println("!");

	}

}　　

import java.util.*;

/**

* This program demonstrates console input.

* @version 1.10 2004-02-10

* @author Cay Horstmann

*/

public class InputTest

{

public static void main(String[] args)

{

Scanner in = new Scanner(System.in);

// get first input

System.out.print("What is your name? ");

String name = in.nextLine();

// get second input

System.out.print("How old are you? ");

int age = in.nextInt();

// display output on console

System.out.println("Hello, " + name + ". Next year, you'll be " + (age + 1));

}

}

import java.io.File;

import java.io.FileNotFoundException;

import java.io.PrintWriter;

import java.util.Scanner;

import java.util.Arrays;

public class WriteReadFileTest {

/**

* @param args

* @throws FileNotFoundException

*/

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

//写入文件演示

PrintWriter out = new PrintWriter("myfile.txt");

out.println("姓名 高数 Java 数据结构 平均成绩 总成绩");

out.println("张三 20 30 40 0 0");

out.println("李四 50 60 70 0 0");

out.close();//切记，输出完毕，需要close

//读入文件演示

Scanner in = new Scanner(new File("myfile.txt"));//为myfile.txt这个File创建一个扫描器in

int number = 1;//行号

while(in.hasNextLine()){//判断扫描器是否还有下一行未读取，该循环把文件的每一行都读出

String line = in.nextLine();//读出myfile.txt的下一行

System.out.println("第"+(number++)+"行的内容" +"="+line);

Scanner linescanner = new Scanner(line);//对每一行的内容建立一个扫描器

linescanner.useDelimiter(" ");//使用空格作为分隔符

String name = linescanner.next();

String math = linescanner.next();

String java = linescanner.next();

String ds = linescanner.next();

String avg = linescanner.next();

String total = linescanner.next();

System.out.println("name="+name+" math="+math+" java="+java+" ds="+ds+" avg"+avg+" total="+total);

}

in.close();//读入完毕，最后需要对其进行close。

}

}

import java.util.*;

/**

* This program demonstrates a <code>while</code> loop.

* @version 1.20 2004-02-10

* @author Cay Horstmann

*/

public class Retirement

{

public static void main(String[] args)

{

// read inputs

Scanner in = new Scanner(System.in);

System.out.print("How much money do you need to retire? ");

double goal = in.nextDouble();

System.out.print("How much money will you contribute every year? ");

double payment = in.nextDouble();

System.out.print("Interest rate in %: ");

double interestRate = in.nextDouble();

double balance = 0;

int years = 0;

// update account balance while goal isn't reached

while (balance < goal)

{

// add this year's payment and interest

balance += payment;

double interest = balance * interestRate / 100;

balance += interest;

years++;

}

System.out.println("You can retire in " + years + " years.");

}

}

import java.util.*;

/**

 * This program demonstrates a <code>do/while</code> loop.

 * @version 1.20 2004-02-10

 * @author Cay Horstmann

 */

public class Retirement2

{

   public static void main(String[] args)

   {

      Scanner in = new Scanner(System.in);

      System.out.print("How much money will you contribute every year? ");

      double payment = in.nextDouble();

      System.out.print("Interest rate in %: ");

      double interestRate = in.nextDouble();

      double balance = 0;

      int year = 0;

      String input;

      // update account balance while user isn't ready to retire

      do

      {

         // add this year's payment and interest

         balance += payment;

         double interest = balance * interestRate / 100;

         balance += interest;

         year++;

         // print current balance

         System.out.printf("After year %d, your balance is %,.2f%n", year, balance);

         // ask if ready to retire and get input

         System.out.print("Ready to retire? (Y/N) ");

         input = in.next();

      }

      while (input.equals("N"));

   }

}

import java.util.*;

/**

 * This program demonstrates a <code>for</code> loop.

 * @version 1.20 2004-02-10

 * @author Cay Horstmann

 */

public class LotteryOdds

{

   public static void main(String[] args)

   {

      Scanner in = new Scanner(System.in);

      System.out.print("How many numbers do you need to draw? ");

      int k = in.nextInt();

      System.out.print("What is the highest number you can draw? ");

      int n = in.nextInt();

      /*

       * compute binomial coefficient n*(n-1)*(n-2)*...*(n-k+1)/(1*2*3*...*k)

       */

      int lotteryOdds = 1;

      for (int i = 1; i <= k; i++)

         lotteryOdds = lotteryOdds * (n - i + 1) / i;

      System.out.println("Your odds are 1 in " + lotteryOdds + ". Good luck!");

   }

}