java io简单读写

//读
Reader reader = null;
//写
Writer fw = null;
try{
reader = new FileReader("读取文件位置");
char ch[] = new char[20];

StringBuffer sb = new StringBuffer();
int length  = reader.read(ch);
while(length!=-1){
sb.append(ch,0,length);
length = reader.read(ch);
}

System.out.println(sb.toString());

fw = new FileWriter("写入文件位置");

fw.write(str);
System.out.println("写入完成");
}catch(Exception e){
e.printStackTrace();
}finally{
try{
if(reader!=null){
reader.close();
}
if(fw!=null){
fw.close();
}
}catch(Exception e){
e.printStackTrace();
}
}