java 安卓开发之文件的读与写

java文件的读与写，代码：

String file="user.txt";
private void writeFileData(String str1, String str2) throws IOException {
		// TODO Auto-generated method stub

		FileOutputStream outputStream = openFileOutput(file,
                Activity.MODE_PRIVATE);
		outputStream.write(str1.getBytes());
		outputStream.write("#".getBytes());
		outputStream.write(str2.getBytes());
		outputStream.flush();
        outputStream.close();
        Toast.makeText(helloworld.this, "保存成功", Toast.LENGTH_LONG).show();
	}
private String readFileData(String file) throws IOException {
		// TODO Auto-generated method stub

		String display;
		FileInputStream inputStream = this.openFileInput(file);
		byte[] bytes = new byte[1024];
		 ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();
         while (inputStream.read(bytes) != -1) {
             arrayOutputStream.write(bytes, 0, bytes.length);
         }
         inputStream.close();
         display = new String(arrayOutputStream.toByteArray());
         return display;
	}

　　值得注意的是在读取文件的时候，display后跟了空格，在进行字符串比较的时候必须去掉这个空格，即用trim（）方法。

    private void login() throws IOException {
        // TODO Auto-generated method stub
        getData();
        String str=readFileData(file);
        String[] strarray=str.split("#");
        String str0=strarray[].trim();
        String str1=strarray[].trim();
        if(str0.equals(str_name)&&str1.equals(str_pd))
            Toast.makeText(helloworld.this, "登录成功 ",Toast.LENGTH_LONG).show();
        else
            Toast.makeText(helloworld.this, "登录失败 ",Toast.LENGTH_LONG).show();
    }

如上代码所示。str1必须加trim(),不然str1.equals(str_pd)会返回为false。