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convert portion of byte array values to String

I have loaded the entire file into a byte[] array using following code:
byte[] data = Files.readAllBytes(path);
Now i would like to get the first 120 characters as String and any string info from from index and to index.
Could you please let me know how to do it?
Thanks.

Sounds like you're just looking for this constructor:
String text = new String(data, 0, 120, StandardCharsets.UTF_8);
(Always specify the encoding explicitly when converting between binary and text forms.)

How to parse a proxy socks packet in java?

Im trying to build a basic proxy 4 server, and I have to parse a packet and extract its informations that looks like this:
1 byte (version)
1 byte (command)
2 byte (port)
4 byte (ip)
X byte (userID, builds a string by looping until '\0' is found)
Here's my code so far:
InputStream reader = socket.getInputStream();
byte[] ver = new byte[1];
byte[] cmd = new byte[1];
byte[] port = new byte[2];
byte[] ip = new byte[4];
reader.read(ver, 0, 1); //should be: 4
reader.read(cmd, 1, 1); //should be: 1
reader.read(port, 2, 2); //should be: 00, 80
reader.read(ip, 4, 4); //should be: 217, 70, 182, 162
Here's the response I get from my code: [4, 1, 0, 80, -39, 70, -74, -94]
For some reason the IP part I get is always wrong, I really don't know why. My second issue would be: Is there an easy and clean way to get the last userID string part, without having to build a messy loop that could end up hanging for ever, if the \0 byte was not found?

Throw it all away and use the methods of DataInputStream. They will give you ints, shorts, longs, and fully-read byte arrays, and take care of network byte ordering for you as well.

The first issue which you received is all because of byte-overflow and hence,turning to negative numbers as byte ranges from -128 to 127 in Java.
Check this question which I asked on this forum to know about the magic(issues) of byte[]...
Seriously,if this is your approach for last-field,(ip)---I am sure you're not going to get correct answer using direct reforms on byte. The possible solution seems to use other approach like storing in temporary int[], like
int[] ip = new int[4];
byte[] temp = new byte[4];
reader.read(temp, 4, 4); //should be: 217, 70, 182, 162
for(int i=0;i<temp.length;i++)
{
if(temp[i]<0)
ip[i]=(int)(256+temp[i]); // careful here
else
ip[i]=(int)temp[i];
}
And,for the second issue,I think that better solution is get length of String-part using String.length().
int len = userID.length(); // assume user-id would be String type
userid = new byte[len]; // notice the difference between userid and userID
reader.read(userid,0,len);
// I am confused as to how are you reading input from user,
// if you clarify further,I'll update my answer...

Merge three ByteArrays together and then split resulting ByteArrays

I have a ByteArray value as avroBinaryValue , Schema Name value as String schemaName and Last Modified Date value as lastModifiedDate in long.
byte[] avroBinaryValue = os.toByteArray();
String schemaName = "DEMOGRAPHIC";
long lastModifiedDate = "1379811105109";
Now I am planning to convert schemaName into byteArray as well. Let's name it byteSchmeName.
After that, I will convert lastModifiedDate to byteArray as well. let's name that as well to byteLMD.
Now what's the best way to concatenate these three byteArrays together.
avroBinaryValue + byteSchemaName + byteLMD
Secondly, after concatenating these three byteArrays together, I want to split the resulting byteArrays in such a way such that I will be able to get all the three respective byteArrays properly...
Is it possible to do that? Any help will be appreciated.
NOTE:-
All the three byteArrays value will be different in different scenarios.. I am looking the most efficient way to store the resulting byteArrays in such a way such that it doesn't take that much space on the disk. I dont want to serialize it again since avroBinaryValue that I am getting is coming from Avro Data Serialization.. So I want to convert the other two things as well in ByteArray so that I can merge all three together into a single ByteArray.

You need to define a format. You have the following
byte[] avroBinaryValue = os.toByteArray();
String schemaName = "DEMOGRAPHIC";
long lastModifiedDate = 1379811105109L;
I guess avroBinaryValue can be variable length and so can schemaName. For all intents and purposes, lastModifiedDate fits in a long, ie. 8 bytes.
If you want to serialize this (other than using Serializable), you'll have to use a specific format that will tell you what you are reading and when to stop readin it. For example
Offset Length (in bytes) Purpose
0 4 - length of avroBinaryValue array
4 X - avroBinaryValue array
4+X 4 - length of of schemaName byte array
4+X+4 Y - schemaName byte array
4+X+4+Y 8 - value of lastModifiedDate
Also decide if you want big-endian or small-endian byte order.
So you write your three fields as described in the format and you read it the same way.
Here's an example done in memory where os is a String (for simplicity)
public static void main(String[] args) throws Exception {
String os = "whatever os is";
byte[] avroBinaryValue = os.getBytes();
String schemaName = "DEMOGRAPHIC";
long lastModifiedDate = 1379811105109L;
byte[] schemaNameBytes = schemaName.getBytes();
ByteArrayOutputStream byteOs = new ByteArrayOutputStream();
DataOutputStream out = new DataOutputStream(byteOs);
out.writeInt(avroBinaryValue.length);
out.write(avroBinaryValue);
out.writeInt(schemaNameBytes.length);
out.write(schemaNameBytes);
out.writeLong(lastModifiedDate);
// write done
byte[] allWrittenBytes = byteOs.toByteArray();
DataInputStream in = new DataInputStream(new ByteArrayInputStream(allWrittenBytes));
int sizeAvro = in.readInt();
avroBinaryValue = new byte[sizeAvro];
in.read(avroBinaryValue, 0, sizeAvro);
int sizeSchema = in.readInt();
schemaNameBytes = new byte[sizeSchema];
in.read(schemaNameBytes, 0, sizeSchema);
lastModifiedDate = in.readLong();
// read done
System.out.println(new String(avroBinaryValue));
System.out.println(new String(schemaNameBytes));
System.out.println(lastModifiedDate);
}
It prints
whatever os is
DEMOGRAPHIC
1379811105109
I understand you are trying to save space, but it might just be better to write each field to its own column or use a standard format like XML or JSON to serialize your fields.

Convert a String to a byte array and then back to the original String

Is it possible to convert a string to a byte array and then convert it back to the original string in Java or Android?
My objective is to send some strings to a microcontroller (Arduino) and store it into EEPROM (which is the only 1  KB). I tried to use an MD5 hash, but it seems it's only one-way encryption. What can I do to deal with this issue?

I would suggest using the members of string, but with an explicit encoding:
byte[] bytes = text.getBytes("UTF-8");
String text = new String(bytes, "UTF-8");
By using an explicit encoding (and one which supports all of Unicode) you avoid the problems of just calling text.getBytes() etc:
You're explicitly using a specific encoding, so you know which encoding to use later, rather than relying on the platform default.
You know it will support all of Unicode (as opposed to, say, ISO-Latin-1).
EDIT: Even though UTF-8 is the default encoding on Android, I'd definitely be explicit about this. For example, this question only says "in Java or Android" - so it's entirely possible that the code will end up being used on other platforms.
Basically given that the normal Java platform can have different default encodings, I think it's best to be absolutely explicit. I've seen way too many people using the default encoding and losing data to take that risk.
EDIT: In my haste I forgot to mention that you don't have to use the encoding's name - you can use a Charset instead. Using Guava I'd really use:
byte[] bytes = text.getBytes(Charsets.UTF_8);
String text = new String(bytes, Charsets.UTF_8);

You can do it like this.
String to byte array
String stringToConvert = "This String is 76 characters long and will be converted to an array of bytes";
byte[] theByteArray = stringToConvert.getBytes();
http://www.javadb.com/convert-string-to-byte-array
Byte array to String
byte[] byteArray = new byte[] {87, 79, 87, 46, 46, 46};
String value = new String(byteArray);
http://www.javadb.com/convert-byte-array-to-string

Use [String.getBytes()][1] to convert to bytes and use [String(byte[] data)][2] constructor to convert back to string.

byte[] pdfBytes = Base64.decode(myPdfBase64String, Base64.DEFAULT)

import java.io.FileInputStream;
import java.io.ByteArrayOutputStream;
public class FileHashStream
{
// write a new method that will provide a new Byte array, and where this generally reads from an input stream
public static byte[] read(InputStream is) throws Exception
{
String path = /* type in the absolute path for the 'commons-codec-1.10-bin.zip' */;
// must need a Byte buffer
byte[] buf = new byte[1024 * 16]
// we will use 16 kilobytes
int len = 0;
// we need a new input stream
FileInputStream is = new FileInputStream(path);
// use the buffer to update our "MessageDigest" instance
while(true)
{
len = is.read(buf);
if(len < 0) break;
md.update(buf, 0, len);
}
// close the input stream
is.close();
// call the "digest" method for obtaining the final hash-result
byte[] ret = md.digest();
System.out.println("Length of Hash: " + ret.length);
for(byte b : ret)
{
System.out.println(b + ", ");
}
String compare = "49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d";
String verification = Hex.encodeHexString(ret);
System.out.println();
System.out.println("===")
System.out.println(verification);
System.out.println("Equals? " + verification.equals(compare));
}
}

How best to convert a byte[] array to a string buffer

I have a number of byte[] array variables I need to convert to string buffers.
is there a method for this type of conversion ?
Thanks
Thank you all for your responses..However I didn't make myself clear....
I'm using some byte[] arrays pre-defined as public static "under" the class declaration
for my java program. these "fields" are reused during the "life" of the process.
As the program issues status messages, (written to a file) I've defined a string buffer
(mesg_data) that used to format a status message.
So as the program executes
I tried msg2 = String(byte_array2)
I get a compiler error:
cannot find symbol
symbol : method String(byte[])
location: class APPC_LU62.java.LU62XnsCvr
convrsID = String(conversation_ID) ;
example:
public class LU62XnsCvr extends Object
.
.
static String convrsID ;
static byte[] conversation_ID = new byte[8] ;
So I can't use a "dynamic" define of a string variable because the same variable is used
in multiple occurances.
I hope I made myself clear
Thanks ever so much
Guy

String s = new String(myByteArray, "UTF-8");
StringBuilder sb = new StringBuilder(s);

There is a constructor that a byte array and encoding:
byte[] bytes = new byte[200];
//...
String s = new String(bytes, "UTF-8");
In order to translate bytes to characters you need to specify encoding: the scheme by which sequences (typically of length 1,2 or 3) of 0-255 values (that is: sequence of bytes) are mapped to characters. UTF-8 is probably the best bet as a default.

You can turn it to a String directly
byte[] bytearray
....
String mystring = new String(bytearray)
and then to convert to a StringBuffer
StringBuffer buffer = new StringBuffer(mystring)

You may use
str = new String(bytes)
By thewhat the code above does is to create a java String (i.e. UTF-16) with the default platform character encoding.
If the byte array was created from a string encoded in the platform default character encoding this will work well.
If not you need to specify the correct character encoding (Charset) as
String str = new String (byte [] bytes, Charset charset)

It depends entirely on the character encoding, but you want:
String value = new String(bytes, "US-ASCII");
This would work for US-ASCII values.
See Charset for other valid character encodings (e.g., UTF-8)