Java基础巩固系列 RandomAccessFile（随机访问文件）

代码示例：

[code]/*
* RandomAccessFile:支持随机访问
* 1.既可以充当一个输入流，又可以充当一个输出流
* 2.支持从文件的开头读取、写入
* 3.支持从任意位置的读取、写入（插入）
* */
public class TestRandomAccessFile {

//相较于test3，更通用
@Test
public void test4() {
RandomAccessFile raf = null;
try {
raf = new RandomAccessFile(new File("hello1.txt"), "rw");

raf.seek(4);
byte[] b = new byte[10];
int len;
StringBuffer sb = new StringBuffer();
while ((len = raf.read(b)) != -1) {
sb.append(new String(b, 0, len));
}
raf.seek(4);
raf.write("xy".getBytes());
raf.write(sb.toString().getBytes());
} catch (IOException e) {
e.printStackTrace();
} finally {
if (raf != null) {
try {
raf.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

//实现插入的效果，在d字符后面插入“xy”但多行的文本不太适用会把换行符“吃”了
@Test
public void test3() {
RandomAccessFile raf = null;
try {
raf = new RandomAccessFile(new File("hello1.txt"), "rw");

raf.seek(4);
String str = raf.readLine(); //efg123456
//            long l = raf.getFilePointer();
//            System.out.println(l);
raf.seek(4);
raf.write("xy".getBytes());
raf.write(str.getBytes());
} catch (IOException e) {
e.printStackTrace();
} finally {
if (raf != null) {
try {
raf.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

//实现的实际上是覆盖的效果
@Test
public void test2() {
RandomAccessFile raf = null;
try {
raf = new RandomAccessFile(new File("hello1.txt"), "rw");

raf.seek(4);
raf.write("xy".getBytes());
} catch (IOException e) {
e.printStackTrace();
} finally {
if (raf != null) {
try {
raf.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

//进行文件的读、写
@Test
public void test1() {
RandomAccessFile raf1 = null;
RandomAccessFile raf2 = null;
try {
raf1 = new RandomAccessFile(new File("hello.txt"), "r");
raf2 = new RandomAccessFile(new File("hello1.txt"), "rw");

byte[] b = new byte[20];
int len;
while ((len = raf1.read(b)) != -1) {
raf2.write(b, 0, len);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (raf2 != null) {
try {
raf2.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (raf1 != null) {
try {
raf1.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

}

}