在java中，如何从输入流中读取固定长度并保存为文件？例如。我想从 inputStream 读取 5M，并保存为 downloadFile.txt 或其他内容。(BUFFERSIZE=1024)
FileOutputStream fos = new FileOutputStream(downloadFile);
byte buffer [] = new byte[BUFFERSIZE];
int temp = 0;
while ((temp = inputStream.read(buffer)) != -1)
{
fos.write(buffer, 0, temp);
}
java inputstream outputstream fileinputstream fileoutputstream
我正在使用org.apache.commons.net.ftp远程机器下载文件.有一种方法可以将文件读取到FileOutputStream对象中.
ftpClient.retrieveFile("/" + ftpFile.getName(), fos);
问题,这是,我有另一个接受File对象的方法.所以,我需要创建一个File目标文件FileOutputStream.我想,我需要创建一个InputStream能够从中创建文件对象FileOutputStream.它是否正确？我可能会遗漏一些东西,应该有一个简单的方法来创建File一个FileOutputStream？
下一行的Ascii值是10.所以我尝试了这个......
FileOutputStream os = new FileOutputStream(f, true);
os.write(10); // this should get me to next line ?
os.write(b); // b is a byte array...
我正在我的应用程序中实现SSL证书和密钥.我使用CertAndKeyGen类创建了私钥.我试图用密码加密私钥,我通过PBE和Cipher类实现了它.我想将加密的私钥写入PEM格式的文件中.我尝试使用FileOutputStream,但PrintWriter不能正常工作.
以下是我的代码,
final CertAndKeyGen keypair = new CertAndKeyGen("RSA", "SHA1WithRSA", null);
keypair.generate(1024);
final PrivateKey privKey = keypair.getPrivateKey();
byte[] encodedprivkey = privKey.getEncoded();
String MYPBEALG = "PBEWithSHA1AndDESede";
String password = "test123";
int count = 20;// hash iteration count
Random random = new Random();
byte[] salt = new byte[8];
random.nextBytes(salt);
PBEParameterSpec pbeParamSpec = new PBEParameterSpec(salt, count);
PBEKeySpec pbeKeySpec = new PBEKeySpec(password.toCharArray());
SecretKeyFactory keyFac = SecretKeyFactory.getInstance(MYPBEALG);
SecretKey pbeKey = keyFac.generateSecret(pbeKeySpec);
Cipher pbeCipher = Cipher.getInstance(MYPBEALG);
// Initialize PBE Cipher with key and parameters
pbeCipher.init(Cipher.ENCRYPT_MODE, pbeKey, pbeParamSpec); …我正在尝试将日志语句写入SD卡.我决定这样做的方法是通过Application Object在SD卡上创建一个文件.这样我就可以从应用程序的任何地方调用静态方法logToSdcard().
创建了包含文件夹"/ RR3log /",但我记录的每个语句都在其自己的文件中,名为"rr3LogFile.txt".所以我有多个rr3LogFile文件,每个文件包含一个staement.
如何将所有语句写入一个rr3LogFile文件？在此先感谢马特.
public class NfcScannerApplication extends Application{
@Override
public void onCreate() {
super.onCreate();
File storageDir = new File(Environment
.getExternalStorageDirectory(), "/RR3log/");
storageDir.mkdir();
try {
if(outfile == null){
outfile=File.createTempFile("rr3LogFile", ".txt",storageDir);
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void logToSdcard(String tag, String statement){
Log.e(TAG, "inside logtosdcard$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$");
String state = android.os.Environment.getExternalStorageState();
if(!state.equals(android.os.Environment.MEDIA_MOUNTED)) {
try {
throw new IOException("SD Card is not mounted. It is " + state + ".");
} catch …我正在尝试使用progressbar修改下载示例中的koush代码,使其写入FileOutputStream而不是File,但eclipse会给我以下错误:
对于ResponseFuture类型,方法progressHandler(new ProgressCallback(){})未定义
这是代码:
File file = new File(DownloadPath, uri.getLastPathSegment());
FileOutputStream fos = null;
try {
fos = new FileOutputStream(file);
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
}
Future<FileOutputStream> downloading = Ion.with(getApplicationContext())
.load(uri)
.write(fos)
.progressHandler(new ProgressCallback() {
@Override
public void onProgress(int downloaded, int total) {
// inform the progress bar of updates in progress
}
})
.setCallback(new FutureCallback<FileOutputStream>() {
@Override
public void onCompleted(Exception e, FileOutputStream file) {
// download done...
// do stuff with the File or …以下代码尝试将换行符引入字节数组并将字节数组写入文件。
import java.io.*;
public class WriteBytes {
public static void main(String args[]) {
byte[] cities = { 'n', 'e', 'w', 'y', 'o', 'r', 'k', '\n', 'd', 'c' };
FileOutputStream outfile = null;
try {
outfile = new FileOutputStream("newfile.txt");
outfile.write(cities);
outfile.close();
}
catch (Exception e) {
e.printStackTrace();
}
}
}
新文件的内容是：newyorkdc
我所期望的是：
纽约
特区
我尝试打字'\n'但(byte)'\n'无济于事。
解决方案：将数组初始化改为
byte[] cities = { 'n', 'e', 'w', 'y', 'o', 'r', 'k', '\r','\n', 'd', 'c' };
我使用 Notepad++ 查看文件的内容。我想它抑制了换行符，但接受了回车符和换行符组合。
public class JavaCopyFileProgram {
public static void main(String[] args)
{
File sourceFile = new File("F:/Study/Java/Java Programs/Factory Methods.txt");
File destFile = new File("D:/DestFile.txt");
FileInputStream inStream = null;
FileOutputStream outStream = null;
try
{
inStream = new FileInputStream(sourceFile);
outStream = new FileOutputStream(destFile);
byte[] buffer = new byte[1024];
int length;
while ((length = inStream.read(buffer)) != -1)
{
outStream.write(buffer, 0, length);
}
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
try
{
inStream.close();
outStream.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
System.out.println("Success"); …在对我的上一个问题没有回答之后,我将这个问题重新表述为最简单的形式.1个按钮,1个clicklistener,1个可序列化对象和1个子程序,用于输出可序列化对象.此代码基于我在stackoverflow上找到的大约6-8个示例.但它仍然很简单它仍然会产生这个错误:W/System.err(228):java.io.NotSerializableException:serobj.testActivity所以我挑战你,哦,这么明智的代码大师:为什么这段代码会产生这个错误？最重要的是我该怎么做才能解决它？整个代码后跟log输出:
package serobj;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import ser.obj.R;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
public class testActivity extends Activity {
/** Called when the activity is first created. */
public class Tester implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
public String frog;
public Tester(){
frog="frog";
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button button1 = (Button) findViewById(R.id.button1);
button1.setOnClickListener(new View.OnClickListener() …我试过很多方法将我的sqlite db文件复制到我的/ data/data/packagename/databases文件夹,但是我仍然陷入FileNotFoundException,由FileOutputStream对象触发...这是代码:
public static boolean checkCopyDb(Context c, DbHandler _db) {
try {
String destPath = "/data/data/" + c.getPackageName() + "/databases/db_sociallibraries.db";
File dbFile = new File(destPath);
if(!dbFile.exists()) {
_db.copyDb(c.getAssets().open(DB_NAME), new FileOutputStream(destPath)); // Line 44 - Throws the exception
}
return true;
}
catch (IOException e) {
e.printStackTrace();
return false;
}
}
private void copyDb(InputStream inputStream, OutputStream outputStream) throws IOException {
byte[] buffer = new byte[1024];
int length;
while((length = inputStream.read(buffer)) > 0) {
outputStream.write(buffer,0,length);
}
inputStream.close();
outputStream.close();
}
这是错误:
02-09 …
sqlite android assets filenotfoundexception fileoutputstream
fileoutputstream ×10
java ×6
android ×4
outputstream ×2
arrays ×1
assets ×1
download ×1
file-io ×1
inputstream ×1
ion-koush ×1
printwriter ×1
sd-card ×1
serializable ×1
sqlite ×1