Java|Java IO中的其他读写流 JavaIO中的其他读写流

RandomAccessFile

构造方法

//var1 文件路径,var 文件的读写模式 "r"只读，"w"只写，"rw"读写 public RandomAccessFile(String var1, String var2) throws FileNotFoundException { this(var1 != null?new File(var1):null, var2); } //传文件，和模式 public RandomAccessFile(File var1, String var2) throws FileNotFoundException {}
【Java|Java IO中的其他读写流】其他常用方法

public void close () 关闭操作public int read ( byte[] b)将内容读取到一个byte数组之中public final byte readByte () 读取一个字节public final int readInt () 从文件中读取整型数据。public void seek ( long pos)设置读指针的位置。public final void writeBytes (String s)将一个字符串写入到文件之中，按字节的方式处理。public final void writeInt ( int v)将一个int型数据写入文件，长度为4位。public int skipBytes ( int n)指针跳过多少个字节。

RandomAccessFile 读写案例

文件路径

//文件路径 public static final String PATH = "/Volumes/huang/studyfromGitHub/JavaForAndroid/JavaForAndroid/series11/src/main/java/files/testRAF.txt";
写

/** * */ private static void testWrite() { RandomAccessFile accessFile = null; try { //读写模式创建实例 accessFile = new RandomAccessFile(PATH, "rw"); //读取文件长度 System.out.println(accessFile.length() + " B"); //0B//将文件指针移动中间位置 accessFile.seek(accessFile.length() / 2); String name = null; int age = 0; // int 的长度为4 float money = 1.2f; // float 的长度为4 //double长度为8name = "name1"; // 长度为5de字符串 age = 20; money = 23.5f; accessFile.writeBytes(name); //读取文件长度 System.out.println(accessFile.length() + "B"); //5B accessFile.writeInt(age); System.out.println(accessFile.length() + "B"); //9B accessFile.writeFloat(money); System.out.println(accessFile.length() + "B"); //13B System.out.println("================================"); name = "name2"; // 长度为5de字符串 age = 21; money = 24.5f; accessFile.writeBytes(name); System.out.println(accessFile.length() + "B"); //18B accessFile.writeInt(age); System.out.println(accessFile.length() + "B"); //22B accessFile.writeFloat(money); System.out.println(accessFile.length() + "B"); //26B//accessFile.writeUTF("hello，你好！"); //注：从中间写入的数据是覆盖后面的内容，因此在写数据时，尽量追加在内容之后 } catch (Exception e) { e.printStackTrace(); } finally { try { accessFile.close(); } catch (IOException e) { e.printStackTrace(); } } }
读

/** * 读 */ private static void testRead() { RandomAccessFile accessFile = null; //读写模式创建实例 try { accessFile = new RandomAccessFile(PATH, "r"); //只读模式创建实例 String name = null; int age = 0; float money = 0.0f; byte[] bytes = new byte[5]; //假如要先读第二个人的信息 accessFile.skipBytes(13); //则跳过前13字节 for (int i = 0; i < bytes.length; i++) { bytes[i] = accessFile.readByte(); //读取一个字节 } name = new String(bytes); age = accessFile.readInt(); money = accessFile.readFloat(); System.out.println("name2:-->" + name + "\t" + age + "\t" + money); //读第一个 accessFile.seek(0); //指针回到0 //假如要先读第二个人的信息 for (int i = 0; i < bytes.length; i++) { bytes[i] = accessFile.readByte(); //读取一个字节 } name = new String(bytes); age = accessFile.readInt(); money = accessFile.readFloat(); System.out.println("name1:-->" + name + "\t" + age + "\t" + money); } catch (Exception e) { e.printStackTrace(); }finally { try { accessFile.close(); } catch (IOException e) { e.printStackTrace(); } } }
读的运行结果

DataOutputStream(数据输出流)、DataInputStream(数据输入流) DataOutputStream 构造方法

//传入一个字节输出流 public DataOutputStream(OutputStream var1) { super(var1); }

用法案例

文件路径

public static final String PATH = "/Volumes/huang/studyfromGitHub/JavaForAndroid/JavaForAndroid/series11/src/main/java/files/testOutput.txt";
写

/** * DataOutputStream 写 */ private static void write() { DataOutputStream outputStream = null; try { //传入字节流实例获取对象实例 outputStream = new DataOutputStream(new FileOutputStream(PATH)); //写入基本数据 outputStream.writeUTF("你好，Java"); //写入utf-8编码字符串 outputStream.writeInt(10); outputStream.writeInt(34); outputStream.writeChar('a'); outputStream.writeBoolean(true); } catch (Exception e) { e.printStackTrace(); }finally { try { outputStream.close(); } catch (IOException e) { e.printStackTrace(); } } }
读

/** * */ private static void read() { DataInputStream inputStream=null; try { inputStream=new DataInputStream(new FileInputStream(PATH)); //2. 读取数据 String txt=inputStream.readUTF(); //读取utf-8编码的字符串 int a=inputStream.readInt(); int b=inputStream.readInt(); int num=inputStream.readChar(); boolean flag=inputStream.readBoolean(); System.out.println(txt+"\r\n"+a+" "+b+","+num+","+flag); } catch (Exception e) { e.printStackTrace(); }finally { //关闭流 try { inputStream.close(); } catch (IOException e) { e.printStackTrace(); } } }
读结果

ByteArrayInputStream、ByteArrayOutputStream很常用的两个类 ByteArrayInputStream 构造方法

//使用一个字节数组当中所有的数据做为数据源 public ByteArrayInputStream(byte[] var1) { ..... } //从数组当中的第offset开始，一直取出length个这个字节做为数据源。 public ByteArrayInputStream(byte[] var1, int var2, int var3) { .... }

ByteArrayOutputStream 构造方法

//创建一个32个字节的缓冲区 public ByteArrayOutputStream() { this(32); } //根据参数指定大小创建缓冲区 public ByteArrayOutputStream(int var1) { if(var1 < 0) { throw new IllegalArgumentException("Negative initial size: " + var1); } else { this.buf = new byte[var1]; } }

这两个构造函数创建的缓冲区大小在数据过多的时候都会自动增长。
案例运用

/** * ByteArrayOutputStream拷贝本文件内容 */ public class Demo9 { //源文件路径 public static final String sourcePath = "/Volumes/huang/studyfromGitHub/JavaForAndroid/JavaForAndroid/series11/src/main/java/com/example/Demo9.java"; public static void main(String[] args) { try { //得到字节流 FileInputStream inputStream = new FileInputStream(sourcePath); //将字节流转成字符流 InputStreamReader inputStreamReader = new InputStreamReader(inputStream); //将字节流包装成一个缓冲字符流 BufferedReader bufferedReader = new BufferedReader(inputStreamReader); //创建内存流对象--内存输出流 ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream(inputStream.available()); //将字节流转换成字符流 OutputStreamWriter outputStreamWriter = new OutputStreamWriter(arrayOutputStream); //将字符流包装成缓冲字符流--BufferedWriter BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter); String msg = null; while ((msg = bufferedReader.readLine()) != null) { bufferedWriter.write(msg); //向内存中写入数据 bufferedWriter.newLine(); bufferedWriter.flush(); //将缓冲区的数据写入到内存流中使用的内存区中 } byte[] bytes = arrayOutputStream.toByteArray(); System.out.println(new String(bytes)); //关闭流 bufferedReader.close(); bufferedWriter.close(); } catch (Exception e) { e.printStackTrace(); }} }