java急需关注的知识点-IO流

java需要关注的知识点---IO流
1.无论何时使用readLine().都不应该使用DataInputStream,而应该使用BufferedReader.
2.RandomAccessFile，只有RandomAccessFile支持搜索操作，并且只适用于文件。
到jdk1.4中，它的大部分功能被nio存储映射文件所取代。
3.读文件的几种方式：
缓冲输入文件

public class BufferedInputFile {public static String read(String file) throws IOException{StringBuffer sb = new StringBuffer();FileReader fileReader = new FileReader(file);BufferedReader br = new BufferedReader(fileReader);String s = null;while((s = br.readLine()) != null) {sb.append(s + "\n");}return sb.toString();}public static void main(String[] args) {try {System.out.println(read("D:\\RSA75WP\\test\\src\\com\\io\\BufferedInputFile.java"));} catch (IOException e) {e.printStackTrace();}}}

从内存中输入：

public class MemoryInput {/** * @param args * @throws IOException  */public static void main(String[] args) throws IOException {// TODO Auto-generated method stubStringReader in = new StringReader(BufferedInputFile.read("D:\\RSA75WP\\test\\src\\com\\io\\MemoryInput.java"));int c;while((c = in.read()) != -1) {System.out.print((char)c);}}}

格式化的内存输入：

public class FormattedMemoryInput {/** * @param args * @throws IOException  */public static void main(String[] args) throws IOException {DataInputStream dis = new DataInputStream(new ByteArrayInputStream((BufferedInputFile.read("D:\\RSA75WP\\test\\src\\com\\io\\FormattedMemoryInput.java").getBytes())));try {while(true) {System.out.print((char)dis.readByte());}} catch (Exception e) {System.out.println("End of stream");}}}

使用available的工作方式会随着所读取的媒介类型不同而有所不同，需要小心使用：

public class TestEof {/** * @param args * @throws IOException  */public static void main(String[] args) throws IOException {DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream("D:\\RSA75WP\\test\\src\\com\\io\\TestEof.java")));while (in.available() != 0) {System.out.println((char)in.readByte());}}}

4.写文件：
DataOutputStream:

public class DateOutputStreamTest {public static void main(String[] args) throws IOException {DataOutputStream dops = new DataOutputStream(new BufferedOutputStream(new FileOutputStream("Data.txt")));dops.writeDouble(3.32);dops.writeUTF("test outputStream");dops.writeInt(4);dops.close();DataInputStream dis = new DataInputStream(new BufferedInputStream(new FileInputStream("Data.txt")));System.out.println(dis.readDouble());System.out.println(dis.readUTF());System.out.println(dis.readInt());}}[b]

RandomAccessFile[/b]

public class UsingRandomAccessFile {static String fileNme = "rtest.dat";static void display() throws IOException{RandomAccessFile raf = new RandomAccessFile(fileNme, "r");for ( int i = 0; i< 7 ;i++) {System.out.println("Value:" + i + ":" + raf.readDouble());}System.out.println(raf.readUTF());raf.close();}/** * @param args * @throws IOException  */public static void main(String[] args) throws IOException {RandomAccessFile rf = new RandomAccessFile(fileNme,"rw");for(int i = 0; i < 7; i++)rf.writeDouble(i*1.414);rf.writeUTF("this end of the file");rf.close();display();rf = new RandomAccessFile(fileNme,"rw");rf.seek(5*8);rf.writeDouble(47.0001);rf.close();display();}}

读取二进制文件：

public class BinaryFile {public static byte[] read(File bFile) throws IOException {BufferedInputStream bf = new BufferedInputStream(new FileInputStream(bFile));try {byte[] data = new byte[bf.available()];bf.read(data);return data;}finally{bf.close();}}public static byte[] read(String fileName) throws IOException{return read(new File(fileName).getAbsoluteFile());}}

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