package myprojects.fileio;import java.io.FileReader;public class FileIO {
public FileIO() { } public void getFileStrings() { try { char[] b= new char[100]; FileReader fr = new FileReader("c:/abc.txt"); fr.read(b) ; System.out.println(b); //fr.read(b, 1, 100); } catch (Exception e) { } } public static void main(String args[]) { System.out.println("Starting FileIO..."); FileIO FileIO1 = new FileIO(); FileIO1.getFileStrings(); } }
我认为比较经典的一个I/O的例子,着重看关于IO的代码 //: c12:IOStreamDemo.java // Typical I/O stream configurations. // {RunByHand} // {Clean: IODemo.out,Data.txt,rtest.dat} import com.bruceeckel.simpletest.*; import java.io.*;public class IOStreamDemo { private static Test monitor = new Test(); // Throw exceptions to console: public static void main(String[] args) throws IOException { // 1. Reading input by lines: BufferedReader in = new BufferedReader( new FileReader("IOStreamDemo.java")); String s, s2 = new String(); while((s = in.readLine())!= null) s2 += s + "\n"; in.close(); // 1b. Reading standard input: BufferedReader stdin = new BufferedReader( new InputStreamReader(System.in)); System.out.print("Enter a line:"); System.out.println(stdin.readLine()); // 2. Input from memory StringReader in2 = new StringReader(s2); int c; while((c = in2.read()) != -1) System.out.print((char)c); // 3. Formatted memory input try { DataInputStream in3 = new DataInputStream( new ByteArrayInputStream(s2.getBytes())); while(true) System.out.print((char)in3.readByte()); } catch(EOFException e) { System.err.println("End of stream"); } // 4. File output try { BufferedReader in4 = new BufferedReader( new StringReader(s2)); PrintWriter out1 = new PrintWriter( new BufferedWriter(new FileWriter("IODemo.out"))); int lineCount = 1; while((s = in4.readLine()) != null ) out1.println(lineCount++ + ": " + s); out1.close(); } catch(EOFException e) { System.err.println("End of stream"); } // 5. Storing & recovering data try { DataOutputStream out2 = new DataOutputStream( new BufferedOutputStream( new FileOutputStream("Data.txt"))); out2.writeDouble(3.14159); out2.writeUTF("That was pi"); out2.writeDouble(1.41413); out2.writeUTF("Square root of 2"); out2.close(); DataInputStream in5 = new DataInputStream( new BufferedInputStream( new FileInputStream("Data.txt"))); // Must use DataInputStream for data: System.out.println(in5.readDouble()); // Only readUTF() will recover the // Java-UTF String properly: System.out.println(in5.readUTF()); // Read the following double and String: System.out.println(in5.readDouble()); System.out.println(in5.readUTF()); } catch(EOFException e) { throw new RuntimeException(e); } // 6. Reading/writing random access files RandomAccessFile rf = new RandomAccessFile("rtest.dat", "rw"); for(int i = 0; i < 10; i++) rf.writeDouble(i*1.414); rf.close(); rf = new RandomAccessFile("rtest.dat", "rw"); rf.seek(5*8); rf.writeDouble(47.0001); rf.close(); rf = new RandomAccessFile("rtest.dat", "r"); for(int i = 0; i < 10; i++) System.out.println("Value " + i + ": " + rf.readDouble()); rf.close(); monitor.expect("IOStreamDemo.out"); } } ///:~
toWnyu(西门吹水) 运行错误! Exception in thread "main" java.lang.NoClassDefFoundError: FileIO (wrong name: m yprojects/fileio/FileIO) at java.lang.ClassLoader.defineClass0(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:537) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:12 3) at java.net.URLClassLoader.defineClass(URLClassLoader.java:251) at java.net.URLClassLoader.access$100(URLClassLoader.java:55) at java.net.URLClassLoader$1.run(URLClassLoader.java:194) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:187) at java.lang.ClassLoader.loadClass(ClassLoader.java:289) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274) at java.lang.ClassLoader.loadClass(ClassLoader.java:235) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302) 请按任意键继续 . . .
public FileIO() {
}
public void getFileStrings() {
try {
char[] b= new char[100];
FileReader fr = new FileReader("c:/abc.txt");
fr.read(b) ;
System.out.println(b);
//fr.read(b, 1, 100);
} catch (Exception e) {
}
} public static void main(String args[]) {
System.out.println("Starting FileIO...");
FileIO FileIO1 = new FileIO();
FileIO1.getFileStrings();
}
}
//: c12:IOStreamDemo.java
// Typical I/O stream configurations.
// {RunByHand}
// {Clean: IODemo.out,Data.txt,rtest.dat}
import com.bruceeckel.simpletest.*;
import java.io.*;public class IOStreamDemo {
private static Test monitor = new Test();
// Throw exceptions to console:
public static void main(String[] args)
throws IOException {
// 1. Reading input by lines:
BufferedReader in = new BufferedReader(
new FileReader("IOStreamDemo.java"));
String s, s2 = new String();
while((s = in.readLine())!= null)
s2 += s + "\n";
in.close(); // 1b. Reading standard input:
BufferedReader stdin = new BufferedReader(
new InputStreamReader(System.in));
System.out.print("Enter a line:");
System.out.println(stdin.readLine()); // 2. Input from memory
StringReader in2 = new StringReader(s2);
int c;
while((c = in2.read()) != -1)
System.out.print((char)c); // 3. Formatted memory input
try {
DataInputStream in3 = new DataInputStream(
new ByteArrayInputStream(s2.getBytes()));
while(true)
System.out.print((char)in3.readByte());
} catch(EOFException e) {
System.err.println("End of stream");
} // 4. File output
try {
BufferedReader in4 = new BufferedReader(
new StringReader(s2));
PrintWriter out1 = new PrintWriter(
new BufferedWriter(new FileWriter("IODemo.out")));
int lineCount = 1;
while((s = in4.readLine()) != null )
out1.println(lineCount++ + ": " + s);
out1.close();
} catch(EOFException e) {
System.err.println("End of stream");
} // 5. Storing & recovering data
try {
DataOutputStream out2 = new DataOutputStream(
new BufferedOutputStream(
new FileOutputStream("Data.txt")));
out2.writeDouble(3.14159);
out2.writeUTF("That was pi");
out2.writeDouble(1.41413);
out2.writeUTF("Square root of 2");
out2.close();
DataInputStream in5 = new DataInputStream(
new BufferedInputStream(
new FileInputStream("Data.txt")));
// Must use DataInputStream for data:
System.out.println(in5.readDouble());
// Only readUTF() will recover the
// Java-UTF String properly:
System.out.println(in5.readUTF());
// Read the following double and String:
System.out.println(in5.readDouble());
System.out.println(in5.readUTF());
} catch(EOFException e) {
throw new RuntimeException(e);
} // 6. Reading/writing random access files
RandomAccessFile rf =
new RandomAccessFile("rtest.dat", "rw");
for(int i = 0; i < 10; i++)
rf.writeDouble(i*1.414);
rf.close();
rf = new RandomAccessFile("rtest.dat", "rw");
rf.seek(5*8);
rf.writeDouble(47.0001);
rf.close();
rf = new RandomAccessFile("rtest.dat", "r");
for(int i = 0; i < 10; i++)
System.out.println("Value " + i + ": " +
rf.readDouble());
rf.close();
monitor.expect("IOStreamDemo.out");
}
} ///:~
运行错误!
Exception in thread "main" java.lang.NoClassDefFoundError: FileIO (wrong name: m
yprojects/fileio/FileIO)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:537)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:12
3)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:251)
at java.net.URLClassLoader.access$100(URLClassLoader.java:55)
at java.net.URLClassLoader$1.run(URLClassLoader.java:194)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
请按任意键继续 . . .
无法编译
这个当然无法编译,看第一句import就知道了,没有这个包嘛
我举这个例子的目的是看看I/O的用法
byte流是八位的,字符流是16位的,支持unicode字符集
使用的基本方法是对象组合,其中一些类支持基本的输入输出(FileInputStream,ObjectInputStream等等),其他一些类支持为基本的流添加功能,比如BufferedInputStream就可以为流增加内部缓冲功能从而可以提高性能等等,这些修饰类大都继承自Filter********类
找一个类图看一下,就会很明了,star的例子来自tij吧,楼主可以找一本看看呀