writedata.java

输入五个学生成绩并计算平均数

//输入成绩

import java.io.*;

class WriteData
{
	public static void main(String[] args)
	{
		byte[] byteBuf = new byte[81];//缓冲区
		File file = new File("g:\\data.txt");//输出文件
		FileOutputStream fos = null;//输出流
		try{
			fos = new FileOutputStream(file);
		}
		catch(FileNotFoundException fnfe)
		{
			fnfe.printStackTrace();
		}

		for(int i=0; i<5; i++)//输入成绩
		{
			System.out.print("请输入成绩 " + (i+1) + ":");
			try{
				System.in.read(byteBuf);
				String sTemp = new String(byteBuf);
				sTemp = sTemp.trim() + " ";
				fos.write(sTemp.getBytes());//写入文件
			}
			catch(IOException ioe)
			{
				ioe.printStackTrace();
			}
		}

		try{
			fos.close();//关闭流
			fos = null;
		}
		catch(IOException ioe)
		{
			ioe.printStackTrace();
		}
	}
}

//计算成绩

import java.io.*;
import java.util.*;

class ComputeData
{
	public static void main(String[] args)
	{
		String sTemp;
		try{
			byte[] byteBuffer = new byte[81];//缓冲区
			File file = new File("g:\\data.txt");//输入文件
			FileInputStream fis = new FileInputStream(file);//输入流
			fis.read(byteBuffer);
			fis.close();
			sTemp = new String(byteBuffer);
		}
		catch(IOException ioe)
		{
			ioe.printStackTrace();
			return;
		}

		System.out.println("原始成绩: " + sTemp);
		StringTokenizer st = new StringTokenizer(sTemp, " ");
		double[] dScore = new double[5];
		int iPosition = 0;
	    while (st.hasMoreTokens()) {
	    	String s = st.nextToken();
	    	if(s != null)
	    	{
	    		s = s.trim();
	    	}
	    	if(s.length() > 0)
					dScore[iPosition++] = Double.parseDouble(s);
	     }
		double dSum = 0.0;
		for(int i=0; i<dScore.length; i++)
			dSum += dScore[i];
		System.out.println("平均成绩: " + (dSum/dScore.length));

		bubbleSort(dScore);

		System.out.println();
		System.out.print("排序后成绩: ");
		for(int i=0; i<dScore.length; i++)
		{
			System.out.print(dScore[i] + " ");
		}
		System.out.println();
	}

	//冒泡排序
	public static void bubbleSort(double[] dValue)
	{
		for(int i=0; i<dValue.length; i++)
		{
			for(int j=i; j<dValue.length; j++)
			{
				if(dValue[i] > dValue[j])
				{
					double dTemp = dValue[i];
					dValue[i] = dValue[j];
					dValue[j] = dTemp;
				}
			}
		}
	}

}