Java面向对象编程实例详解
时间:2011-01-16 zdnet 龚赤兵
Java是一种面向对象的语言，是实现面向对象编程的强大工具。但如何在编程中实际运用并发挥其最大效能呢？本文通过一个实际Java程序的开发过程，详细说明了如何使用面向对象实现Java编程。
我们要实现的Java应用程序是：当用户输入一个球体的半径，程序将显示该球体的体积与表面积。在您阅读下文以前，请您自己思考一分钟，您将如何设计该Java应用程序。
一、普通实现方法
我相信大多数程序员要实现上述功能的程序，非常迅速地、自信地将采用下面的实现代码：
class Sphere
{
public static void main(String[] args)
{
EasyReader console = new EasyReader();
System.out.print("Enter the radius: ");
double radius = console.readDouble();
System.out.println("Radius = " + radius);
double volume = 4.0 / 3.0 * Math.PI * radius * radius * radius;
System.out.println("Volume = " + volume);
double surfArea = 4.0 * Math.PI * radius * radius;
System.out.println("Surface area = " + surfArea);
}
}
EasyReader类代码如下：
import java.io.*;
public class EasyReader
{
protected String myFileName;
protected BufferedReader myInFile;
protected int myErrorFlags = 0;
protected static final int OPENERROR = 0x0001;
protected static final int CLOSEERROR = 0x0002;
protected static final int READERROR = 0x0004;
protected static final int EOF = 0x0100;
/**
* Constructor. Prepares console (System.in) for reading
*/
public EasyReader()
{
myFileName = null;
myErrorFlags = 0;
myInFile = new BufferedReader(
new InputStreamReader(System.in), 128);
}
/**
* Constructor. opens a file for reading
* @param fileName the name or pathname of the file
*/
public EasyReader(String fileName)
{
myFileName = fileName;
myErrorFlags = 0;
try
{
myInFile = new BufferedReader(new FileReader(fileName), 1024);
}
catch (FileNotFoundException e)
{
myErrorFlags |= OPENERROR;
myFileName = null;
}
}
/**
* Closes the file
*/
public void close()
{
if (myFileName == null)
return;
try
{
myInFile.close();
}
catch (IOException e)
{
System.err.println("Error closing " + myFileName + "\n");
myErrorFlags |= CLOSEERROR;
}
}
/**
* Checks the status of the file
* @return true if en error occurred opening or reading the file,
* false otherwise
*/
public boolean bad()
{
return myErrorFlags != 0;
}
/**
* Checks the EOF status of the file
* @return true if EOF was encountered in the previous read
* operation, false otherwise
*/
public boolean eof()
{
return (myErrorFlags & EOF) != 0;
}
private boolean ready() throws IOException
{
return myFileName == null || myInFile.ready();
}
/**
* Reads the next character from a file (any character including
* a space or a newline character).
* @return character read or <code>null</code> character
* (Unicode 0) if trying to read beyond the EOF
*/
public char readChar()
{
char ch = ''\u0000'';
try
{
if (ready())
{
ch = (char)myInFile.read();
}
}
catch (IOException e)
{
if (myFileName != null)
System.err.println("Error reading " + myFileName + "\n");
myErrorFlags |= READER
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