txt文本的編碼是ansi，雖然你寫入時設(shè)置了gbk（txt文件中可以正常顯示）但是控制臺輸出的編碼是utf-8和ansi不相符合，所以出現(xiàn)亂碼。個人意見，還請指正.

pppp

oo?o?lo?o
oo?oo
oo
l

oolo

o

lo

ooo?o

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Arrays;
public class RafDome {

?public static void main(String[] args) throws IOException {
??File demo? = new File("demo");
??if(!demo.exists()){
???demo.mkdir();
??}
??File file =new File(demo,"ra.dat");
??if(!file.exists()){
???file.createNewFile();
??}??
??RandomAccessFile raf =new RandomAccessFile(file,"rw");
??System.out.println(raf.getFilePointer())；

??String s="AB123456中國人民政府";
??byte[]? buf =s.getBytes("gbk");
??System.out.println(buf.length);
??raf.write(buf.length);
??raf.write(buf);
??
??raf.seek(0);
??
??byte [] bu? =new byte[（int）raf.read()];??
??raf.read(bu);
??String? str= new? String(bu,"gbk");
??System.out.println(str);
??raf.close();
?}
}

//這里我寫了一個批量寫入和讀取

public?class?RandomAccessFileTest?{
	public?static?void?main(String[]?args)throws?IOException?{
		File?file1=new?File("demo");
		if(!file1.exists())
			file1.mkdir();
		File?file2=new?File(file1,"a.txt");
		if(!file2.exists())
			file2.createNewFile();
		RandomAccessFile?raf?=?new?RandomAccessFile(file2,?"rw");
		//指針的位置
		System.out.println(raf.getFilePointer());
		raf.write('a');//只寫一個字節(jié)
		System.out.println(raf.getFilePointer());
		raf.write('b');
		System.out.println(raf.getFilePointer());
		int?i=0x7fffffff;
		raf.write(i>>>24);//寫入后八位
		System.out.println(raf.getFilePointer());

		raf.write(i>>>16);
		System.out.println(raf.getFilePointer());
		
		raf.write(i>>>8);
		System.out.println(raf.getFilePointer());

		raf.write(i);
		System.out.println(raf.getFilePointer());

		raf.writeInt(i);
		System.out.println(raf.getFilePointer());
		
		String?string="中";
		byte[]?byte1=string.getBytes("gbk");
		raf.write(byte1);//漢字在gbk編碼中占兩個字節(jié)
		System.out.println(raf.getFilePointer());
		System.out.println("顯示該文件的字節(jié)總長度:"+raf.length());

		
		//進(jìn)行讀取操作，一次性將所有內(nèi)容讀取出來
		raf.seek(0);//將指針的指向移動到開頭
		byte[]?byte3=new?byte[(int)raf.length()];
		raf.read(byte3);//將文件的內(nèi)容讀到字節(jié)數(shù)組中
		System.out.println(Arrays.toString(byte3));
		String?string3=new?String(byte3,"gbk");
		System.out.println(string3);
		}
	}

把代碼粘上來

發(fā)源碼來看看，照你直接說的意思應(yīng)該是沒有問題的