作者dasea (植栽雞肉飯)
看板ncyu_phyedu
標題[討論] i/o
時間Sat Jan 30 15:02:45 2010
Java的IO可分為以下幾類。處理byte的類別有:
InputStream, 可作為input使用, 主要的子類別有:
ByteArrayInputStream, 讀入來源為byte array
FileInputStream, 讀入來源為File
ObjectInputStream, 將其他InputStream加工後, 可用來讀入Object
DataInputStream, 將其他InputStream加工後, 可用來讀入int, float, double,
boolean, bye, char等基本資料型態
OutputStream, 可作為input使用, 主要的子類別有:
ByteArrayOutputStream, 輸出到byte array
FileOutputStream, 輸出到File
ObjectOutputStream, 將其他OutputStream加工後, 可用來輸出Object
DataOutputStream, 將其他OutputStream加工後, 可用來寫出int, float, double,
boolean, bye, char等基本資料型態
PrintStream, 可將各種基本資料型態和字串以文字形式輸出, System.out就是一個
PrintStream
處理char的類別有:
Reader, 作為char輸入, 具有將輸入編碼轉為Unicode編碼的能力, 主要的子類別有:
BufferedReader, 具有緩衝功能, 可讓IO比較有效率
CharArrayReader, 由某個字元陣列作為輸入
InputStreamReader, 作為InputStream轉為Reader的介面
FileReader, 由檔案讀入char
Writer, 作為char輸出, 具有將Unicode編碼轉為輸出編的能力, 主要的子類別有:
BufferedWriter, 具有緩衝功能, 可讓IO比較有效率
CharArrayWriter, 輸出到某個字元陣列
OutputStreamWriter, 作為Writer轉到OutputStream的介面
FileWriter, 將char輸出到檔案
處理檔案的類別有:
File, 具有新增刪除檔案, 查詢檔案長度, 查詢檔案屬性, 查詢路徑等功能
範例
/**
* Programming Methodology Homework #2 Example.
* Author: Shiuh-Sheng Yu
* Date: 3/16/1998
* Last updated date: 3/17/1998
*/
import java.io.*;
import java.util.*;
public class H2 {
private static String nextToken(BufferedReader din) throws IOException {
StringBuffer sb = new StringBuffer();
int c;
try {
do {
c = din.read();
} while (c==' ' || c=='\n' || c=='\r' || c=='\t');
while (c!=-1 && c!=' ' && c!='\n' && c!='\t' && c!='\r') {
sb.append((char)c);
c = din.read();
}
} catch (EOFException e) {
}
if (sb.length()==0) {
return "";
}
return sb.toString();
}
private static Matrix readMatrix(BufferedReader din) throws
MalMatrixException, IOException {
String token = nextToken(din);
int x, y;
double[][] data;
if (!token.equals("matrix")) {
throw new MalMatrixException();
}
token = nextToken(din);
try {
x = Integer.parseInt(token);
} catch (NumberFormatException eNum) {
throw new MalMatrixException();
}
token = nextToken(din);
try {
y = Integer.parseInt(token);
} catch (NumberFormatException eNum) {
throw new MalMatrixException();
}
data = new double[x][y];
for (int i=0; i<x; i++) {
for (int j=0; j<y; j++) {
try {
token = nextToken(din);
data[i][j] = Double.valueOf(token).doubleValue();
} catch (NumberFormatException eNum) {
throw new MalMatrixException();
}
}
}
return new Matrix(data);
}
public static void main(String[] args) {
BufferedReader din;
if (args.length != 1) {
System.out.println("Usage: java H2 fname");
System.out.println("where fname is a file contains matrix data.");
System.exit(0);
}
try {
String inputbuf;
din = new BufferedReader(new FileReader(args[0]));
for (;!(inputbuf=nextToken(din)).equals("");) {
if (inputbuf.equals("+")) {
Matrix a = readMatrix(din);
Matrix b = readMatrix(din);
a.print();
a.add(b);
System.out.println("+");
b.print();
System.out.println("=");
a.print();
} else if (inputbuf.equals("*")) {
Matrix a = readMatrix(din);
Matrix b = readMatrix(din);
Matrix c = a.multiply(b);
a.print();
System.out.println("*");
b.print();
System.out.println("=");
c.print();
} else if (inputbuf.equals("value")) {
Matrix a = readMatrix(din);
System.out.println("value of ");
a.print();
System.out.println("=");
System.out.println(a.determinant());
} else {
break;
}
}
} catch (Exception e) {
e.printStackTrace();
System.exit(1);
}
}
}
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