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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 null 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 |= READERROR; } if (ch == '\u0000') myErrorFlags |= EOF; return ch; } /** * Reads from the current position in the file up to and including * the next newline character. The newline character is thrown away * @return the read string (excluding the newline character) or * null if trying to read beyond the EOF */ public String readLine() { String s = null; try { s = myInFile.readLine(); } catch (IOException e) { if (myFileName != null) System.err.println("Error reading " + myFileName + "\n"); myErrorFlags |= READERROR; } if (s == null) myErrorFlags |= EOF; return s; } /** * Skips whitespace and reads the next word (a string of consecutive * non-whitespace characters (up to but excluding the next space, * newline, etc.) * @return the read string or null if trying to read beyond the EOF */ public String readWord() { StringBuffer buffer = new StringBuffer(128); char ch = ' '; int count = 0; String s = null; try { while (ready() && Character.isWhitespace(ch)) ch = (char)myInFile.read(); while (ready() && !Character.isWhitespace(ch)) { count++; buffer.append(ch); myInFile.mark(1); ch = (char)myInFile.read(); }; if (count > 0) { myInFile.reset(); s = buffer.toString(); } else { myErrorFlags |= EOF; } } catch (IOException e) { if (myFileName != null) System.err.println("Error reading " + myFileName + "\n"); myErrorFlags |= READERROR; } return s; } /** * Reads the next integer (without validating its format) * @return the integer read or 0 if trying to read beyond the EOF */ public int readInt() { String s = readWord(); if (s != null) return Integer.parseInt(s); else return 0; } /** * Reads the next double (without validating its format) * @return the number read or 0 if trying to read beyond the EOF */ public double readDouble() { String |