IO简单示例
File类
用于对磁盘上的文件或目录进行操作
直接父类是Object
创建一个文件
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public class FileTest { public static void main(String[] args) throws
IOException { File file = new File("C:/text.txt"); System.out.println(file.createNewFile()); } } |
在一个目录下创建文件
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public class FileTest2 { public static void main(String[] args) throws
IOException { File file = new File("C:/abc"); File file2 = new File(file,"hello.txt"); System.out.println(file2.createNewFile()); File file3 = new File(file,"xyz/world.txt"); System.out.println(file3.createNewFile()); } } |
创建目录操作
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public class FileTest3 { public static void main(String[] args) { File file = new File("C:/abc/xyz/hello"); System.out.println(file.mkdirs()); System.out.println(file.isDirectory()); } } |
列出指定目录下的文件或目录
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public class FileTest4 { public static void main(String[] args) { File file = new File("C:/java"); String[] names = file.list(); for(String name: names) { System.out.println(name); } File[] files = file.listFiles(); for(File f : files) { System.out.println(f.getName()); System.out.println(f.getParent()); } } } |
文件删除操作
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public class FileTest5 { public static void main(String[] args) throws
IOException { File file = new File("C:/abc/xyz/hello/text.txt"); //file.createNewFile(); boolean delete = file.delete(); System.out.println(delete); } } |
文件名过滤操作
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public class FileTest6 { public static void main(String[] args) { File file = new File("C:/java"); /*String[] names = file.list(); for(String name : names) { if(name.endsWith(".java")) { System.out.println(name); } }*/ String[] names = file.list(new FilenameFilter() { @Override public boolean accept(File dir, String
name) { if(name.endsWith(".java")) { return true; } return false; } }); for(String name : names ) { System.out.println(name); } } } |
文件分隔符的使用
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public class FileTest7 { public static void main(String[] args) throws
IOException { //不加盘符表示java安装的默认盘 File file = new File(File.separator + "helo.txt"); System.out.println(file.createNewFile()); } } |
递归的使用（关键在于要先指定一个出口，才不会出现死循环）
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public class Test1 { public static int calc(int num) { if(num ==1 ) return 1; else return num * calc(num - 1); } public static void main(String[] args) { System.out.println(calc(5)); } } |
斐波那契数列
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public class Fabonaci { public int calc(int pos) { if(1 == pos || 2 == pos) return 1; else return calc(pos-1)+calc(pos-2); } private void sysout() { Fabonaci fab = new Fabonaci(); fab.calc(30); } } |
删除指定目录下的所有文件（用递归实现）
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public class FileTest8 { public static void deleteAll(File file) { if(file.isFile() || 0 == file.list().length) { file.delete(); } else { File[] files = file.listFiles(); for(File f : files) { deleteAll(f); f.delete(); } } } public static void main(String[] args) { File file = new File("C:/test"); try { deleteAll(file); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } } |
把指定目录下的文件结构以树的形式打印出来
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public class FileTest9 { // 判断目录或文件所在的层数 private static int times; // 把目录下的文件以树结构的形式打印出来。 static void treeShow(File file) { if (file.isFile() || 0 == file.listFiles().length) { return; } else { File[] files = file.listFiles(); files = sortFile(files); for (File f : files) { StringBuffer sb = new StringBuffer(); if (f.isDirectory()) { sb.append(getTAbs(times)); sb.append(f.getName()); sb.append("\\"); } else { sb.append(getTAbs(times)); sb.append(f.getName()); } System.out.println(sb); if (f.isDirectory()) { times++; treeShow(f); times--; } } } } // 取得每个目录或文件所处层数的缩进 private static String getTAbs(int times) { StringBuffer sb = new StringBuffer(); for (int i = 0; i < times; i++) { sb.append("\t"); } return sb.toString(); } // 把目录下所有文件以目录为先的次序排序 private static File[] sortFile(File[]
files) { List<File> list = new
ArrayList<File>(); for (File f : files) { if (f.isDirectory()) { list.add(f); } } for (File f : files) { if (f.isFile()) { list.add(f); } } return list.toArray(new File[files.length]); } public static void main(String[] args) { File file = new File("C:/xdict"); treeShow(file); } } |
Stream类
从功能上分：输入流（InputStream）和输出流（OutputStream）
从结构上分：字节流(Byte Streams)和字符流(Character Streams)
字节流输入输出的基础是抽象类InputStream和OutputStream
字符流输入输出的基础是抽象类Reader和Writer
流的分类：
节点流：从特定的地方读写的流类。
过滤流：使用节点流作为输入或输出。过滤流是使用一个已存在的输入流或输出流连接创建的。
字节流的使用
FileInputStream类的使用
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public class InputStreamTest { public static void main(String[] args) throws Exception { InputStream is = new FileInputStream("c:/hello.txt"); byte[] buffer = new byte[200]; int length = 0; if (-1 != (length = is.read(buffer, 0, 200))) { String str = new String(buffer,
0, length); System.out.println(str); } is.close(); } } |
FileOutputStream类的使用
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public class OutputStreamTest { public static void main(String[] args) throws
IOException { OutputStream os = new
FileOutputStream("c:/out.txt",true); String str = "\nwelcomle"; byte[] buffer = str.getBytes(); os.write(buffer); os.close(); } } |
BufferedInputStream类，继承自FilterInputStream
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BufferedOutputStream类，继承自FilterOutputStream
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public class BufferedOutputStreamTest { public static void main(String[] args) throws Exception { OutputStream os = new FileOutputStream("1.txt"); BufferedOutputStream bos = new
BufferedOutputStream(os); bos.write("http://www.sina.com.cn".getBytes()); bos.close(); os.close(); } } |
ByteArrayInputStream类
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public class ByteArrayInputStreamTest { public static void main(String[] args) throws Exception { String str = "abcdef"; byte[] byteArr = str.getBytes(); ByteArrayInputStream bais = new
ByteArrayInputStream(byteArr); int c; //一次只读一个字符 while(-1 != (c = bais.read())) { if(0==c) { System.out.println((char)c); } else { System.out.println(Character.toUpperCase((char) c)); } } bais.close(); } } |
ByteArrayOutputStream类
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public class ByteArrayOutputStreamTest { public static void main(String[] args) throws Exception { String str = "hello world welcome"; byte[] arr = str.getBytes(); ByteArrayOutputStream baos = new
ByteArrayOutputStream(); //把字节数组写入到字节数组输出流中 baos.write(arr); //从字节数组输出流中得到字节数组 byte[] result =
baos.toByteArray(); for(byte b : result) { System.out.println((char)b); } OutputStream os = new
FileOutputStream("c:/test.txt"); //把字节数组写入到文件中。 baos.writeTo(os); baos.close(); os.close(); } } |
DataInputStream类，继承自FilterInputStream
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DataOutputStream类，继承自FilterOutputStream
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public class DataOutputStreamTest { public static void main(String[] args) throws Exception { DataOutputStream dos = new
DataOutputStream(new BufferedOutputStream(new FileOutputStream("data.txt"))); byte b = 3; int i = 12; char c = 'c'; float f = 0.3f; dos.writeByte(b); dos.writeInt(i); dos.writeChar(c); dos.writeFloat(f); dos.close(); DataInputStream dis = new DataInputStream(new
BufferedInputStream(new FileInputStream("data.txt"))); System.out.println(dis.readByte()); System.out.println(dis.readInt()); System.out.println(dis.readChar()); System.out.println(dis.readFloat()); dis.close(); } } |
自定义一个ByteArrayInputStream
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public class MyOwnStream { public static void main(String[] args) throws Exception { byte[] bytes = new byte[16]; for (int i = 0; i < bytes.length; i++) { bytes[i] = (byte) i; } MyInputStream myis = new MyInputStream(bytes); int c = 0; while (true) { if (-1 == (c = myis.read())) { break; } System.out.print(c + " "); } myis.close(); } } // 这里使用了装饰者模式 class MyInputStream extends InputStream { protected byte[] buffer; protected int ptr = 0; public MyInputStream(byte[] bytes) { buffer = bytes; } @Override public int read() throws IOException { return (ptr < buffer.length) ? buffer[ptr++] : -1; } } |
重写InputStream类方法完整的例子
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public class MyOwnStream2 extends InputStream { protected byte[] data; protected int ptr = 0; protected int mark = 0; public MyOwnStream2(byte[] bytes) { this.data = bytes; } @Override public int read() throws IOException { return (ptr < data.length) ? data[ptr++] : -1; } @Override public int read(byte[] b, int off, int len) throws
IOException { if (ptr > data.length || len < 0) { return -1; } if ((ptr + len) > data.length) { len = data.length - ptr; } if (0 == len) { return 0; } System.arraycopy(data, ptr, b, off, len); ptr += len; return len; } @Override public long skip(long n) throws
IOException { return super.skip(n); } @Override public int available() throws IOException { return data.length - ptr; } @Override public void close() throws IOException { ptr = data.length; } @Override public synchronized void mark(int readlimit) { this.mark = readlimit; } @Override public synchronized void reset() throws
IOException { if (mark > 0 || mark < data.length) { throw new IOException("The position is invalid."); } ptr = mark; } @Override public boolean markSupported() { return true; } } |
字符流的使用
InputStreamReader
OutputStreamWrite
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public class StreamTest { public static void main(String[] args) throws Exception { FileOutputStream fos = new
FileOutputStream("file.txt"); OutputStreamWriter osw = new
OutputStreamWriter(fos); BufferedWriter bw = new
BufferedWriter(osw); bw.write("http://www.google.com"); bw.write("\n"); bw.write("http://www.baidu.com"); bw.close(); FileInputStream fis = new FileInputStream("file.txt"); InputStreamReader isr = new
InputStreamReader(fis); BufferedReader br = new
BufferedReader(isr); /*System.out.println(br.readLine()); System.out.println(br.readLine()); System.out.println(br.readLine());*/ String str = br.readLine(); while(null != str) { System.out.println(str); str = br.readLine(); } br.close(); } } |
BufferedReader
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public class StreamTest2 { public static void main(String[] args) throws Exception { InputStreamReader isr = new
InputStreamReader(System.in); BufferedReader br = new
BufferedReader(isr); String str; while(null != (str = br.readLine())) { System.out.println(str); } br.close(); } } |
BufferedWrite
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FileOutputStream fos = new FileOutputStream("file.txt"); OutputStreamWriter osw = new
OutputStreamWriter(fos); BufferedWriter bw = new
BufferedWriter(osw); bw.write("http://www.google.com"); bw.write("\n"); bw.write("http://www.baidu.com"); bw.close(); |
FileReader
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public class FileReaderTest { public static void main(String[] args) throws Exception { FileReader fr = new FileReader("src/com/anllin/io3/FileReaderTest.java"); BufferedReader br = new
BufferedReader(fr); String str ; while(null != (str = br.readLine())) { System.out.println(str); } br.close(); } } |
FileWriter
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public class FileWriteTest { public static void main(String[] args) throws Exception { String str = "hello world welcome nice bueaty"; char[] buffer = new char[str.length()]; str.getChars(0,str.length(),buffer,0); FileWriter fr = new FileWriter("file2.txt"); fr.write(buffer); fr.close(); } } |
CharArrayReader
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public class CharArrayReaderTest { public static void main(String[] args) throws Exception { String str = "abcdefghijklmnopqrstuvwxyz"; char[] buffer = new char[str.length()]; str.getChars(0, str.length(),buffer,0); CharArrayReader car = new
CharArrayReader(buffer); int i ; while(-1 != (i = car.read())) { System.out.println((char)i); } car.close(); } } |
字符集的分类：
ASCII GB2312 GBK Unicode iso-8859- 1 UTF-8
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public class CharsetTest { public static void main(String[] args) { SortedMap<String,Charset> map =
Charset.availableCharsets(); Set<String> set = map.keySet(); for(Iterator<String> iter =
set.iterator(); iter.hasNext();) { System.out.println(iter.next()); } } } |
RandomAccessFile类，可以随机对文件进行读写操作。
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public class RandomAccessFileTest { public static void main(String[] args) throws Exception { Person p = new Person(1, "anllin", 170); RandomAccessFile raf = new
RandomAccessFile("person.txt", "rw"); p.write(raf); raf.seek(0);//让读的位置回到文件的开头 Person p2 = new Person(); p2.read(raf); System.out.println(p2.getId() + ", " +
p2.getName() + ", " + p2.getHeight()); } } class Person { int id; String name; double height; public Person() { } public Person(int id, String name,
double height) { this.id = id; this.name = name; this.height = height; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public double getHeight() { return height; } public void setHeight(double height) { this.height = height; } public void write(RandomAccessFile raf) throws Exception { raf.writeInt(id); raf.writeUTF(name); raf.writeDouble(height); } public void read(RandomAccessFile raf) throws Exception { this.id = raf.readInt(); this.name = raf.readUTF(); this.height = raf.readDouble(); } } |
