File file1=new File("test1.txt");
RandomAccessFile in2=new RandomAccessFile(file1,"rw");
后面参数是"rw"他可读可写，用seek（）来设定位置
不过在用readLine()时，非ASCII码（比如中文）会出现乱码现象
不过有办法
用"iso-8859-1"重新编码，然后重新化为String
String s1=in2.readLine();
byte b1[]=s1.getBytes("iso-8859-1");
String s3=new String(b1,"GB2312");//GB2312要看机器的默认编码
数组内存流
这类流的目的地和源都是内存
分别有字节数组和字符数组
File file1=new File("test1.txt");
ByteArrayOutputStream out1=new ByteArrayOutputStream();//new字节输出流
byte[] b1="hello world".getBytes();//字节数组
out1.write(b1);//输出到内存
ByteArrayInputStream in1=new ByteArrayInputStream(out1.toByteArray());//public byte[] toByteArray()可以返回输出流写入到内存缓冲区的全部字节
byte[] b2=new byte[out1.toByteArray().length];//new字节输入流
in1.read(b2);//读入
System.out.println(new String(b2));
CharArrayWriter out2=new CharArrayWriter();//new字符输出流
char[] b3="你好啊".toCharArray();//化为字符数组
out2.write(b3);//写入内存
CharArrayReader in2=new CharArrayReader(out2.toCharArray());//new字符输入流
char[] b4=new char[out2.toCharArray().length];
System.out.println(b3);