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can't figure out initialization error - java [duplicate]

This question already has answers here:
Variable might not have been initialized error
(12 answers)
Closed 5 years ago.
I can not for the life of me figure out why I'm getting a "variable key might not have been initialized" error. I've entered my entire code because if I remove the BufferedReader and set the string equal to I don't get the error. Also, if I leave the BufferedReader part in and remove the StringBuffer part, string key initializes just fine. Please help! New to java (and programming in general).
import java.util.*;
import java.io.*;
public class reverseString {
public static void main(String [] args) {
String abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
String cipher = "";
String input = "";
String newCipher;
String ouput = "";
BufferedReader readerKeyword = null;
String key;
try {
readerKeyword = new BufferedReader(new FileReader("keyword.txt"));
} catch (FileNotFoundException fnfex) {
System.out.println(fnfex.getMessage() + " File not found.");
System.exit(0);
}
try {
while ((key = readerKeyword.readLine()) !=null) {
System.out.println(key);
}
} catch (IOException ioex) {
System.out.println(ioex.getMessage() + " Unable to read file.");
System.exit(0);
}
StringBuffer sb = new StringBuffer();
int len = abc.length();
for(int i = len -1;i>=0;i--)
cipher = cipher + abc.charAt(i);
System.out.println(abc);
System.out.println(cipher);
newCipher = sb.append(key + cipher).toString();
System.out.println(newCipher);
System.out.println(removeDuplicates(newCipher));
}
static String removeDuplicates(String newCipher) {
char[] charArr = newCipher.toCharArray();
Set<Character> charSet = new LinkedHashSet<Character>();
for(char ch : charArr) {
charSet.add(ch);
}
StringBuffer StrBuf = new StringBuffer();
for(char c : charSet) {
StrBuf.append(c);
}
return StrBuf.toString();
}
}
Was is not initialized in the while loop at line28?

IDE and Compiler shows it when it is not guaranteed initialization for safety/precaution. Do this and it should go away,
BufferedReader readerKeyword = null;
String key = null;
However, do make sure that it gets initialized.
It is not guaranteed initialization because it is inside a try-catch block and if you get an exception, you can get by without initialization because, you are handling it.

convert byte array to string in java

I try to convert byte array to string in java using new String( bytes, "UTF-8") method, but they only return the object. like this #AB4634bSbbfa
So, I searched some way to solve this problem.
I finally get valid string array, by converting hex-code to basic-character array.
like this. char[] chars = {"0", "1", ... "e", "f"};
This never happened before why do i have to convert hex-code to get valid string.
Here is method.
byte array which is hashed by Mac-sha-256 with specific key when i hashed.
public static String getHashString() {
String algorithm = "HmacSHA256";
String hashKey = "some_key";
String message = "abcdefg";
String hexed = "";
try {
Mac sha256_HMAC = Mac.getInstance(algorithm);
SecretKeySpec secret_key = new SecretKeySpec(hashKey.getBytes(), algorithm);
sha256_HMAC.init(secret_key);
byte[] hash = sha256_HMAC.doFinal(message.getBytes("UTF-8"));
// it doesn't work for me.
// hexed = new String(hash, "UTF-8");
// it works.
hexed = bytesToHex(hash);
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (InvalidKeyException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
return hexed;
}
public static final char[] HEX_DIGITS = "0123456789abcdef".toCharArray();
public static String bytesToHex(final byte[] data ) {
final int l = data.length;
final char[] hexChars = new char[l<<1];
for( int i=0, j =0; i < l; i++ ) {
hexChars[j++] = HEX_DIGITS[(0xF0 & data[i]) >>> 4];
hexChars[j++] = HEX_DIGITS[0x0F & data[i]];
}
return new String(hexChars);
}
Thanks.

Following is a sample which shows Conversion of Byte array to String :-
public class TestByte
{
public static void main(String[] argv) {
String example = "This is an example";
byte[] bytes = example.getBytes();
System.out.println("Text : " + example);
System.out.println("Text [Byte Format] : " + bytes);
System.out.println("Text [Byte Format] : " + bytes.toString());
String s = new String(bytes);
System.out.println("Text Decryted : " + s);
}}

I'm not sure the string you get in the end is what you're after. I think a common scenario is to use
new BASE64Encoder().encode(hash)
which will return you the hashed message as String.

just do new String(byteArray);

Compare Strings read from txt file in java

I read a string from a txt file and I want compare this string with my reference. But it displays "not ok" and I don't know why.
public class ReadFile {
public static void main(String[] args) {
try {
File file = new File("nh.txt");
FileReader fileReader = new FileReader(file);
StringBuffer stringBuffer = new StringBuffer();
int numCharsRead;
//char[] charArray1 = new char[1024];
char[] charArray = new char[1024];
while ((numCharsRead = fileReader.read(charArray)) > 0) {
stringBuffer.append(charArray, 0, numCharsRead);
}
String resultat = new String(charArray);
String resultat1 = resultat.replaceAll("\\s", "");
System.out.println(resultat1);
String a="Nihao";
if(a.equals(resultat1)){System.out.println("ok");}
else System.out.println("not ok");
fileReader.close();
System.out.println("Contents of file:");
System.out.println(stringBuffer.toString());
} catch (IOException e) {
e.printStackTrace();
}
}
}

This is because the string resultat1 is a 1024 char length, its possible to a java string to have \0, its in memory like this (if the file contains Niaho):
Nihao\0\0\0..
And because \0 is not a whitespace, this will not make any change:
resultat.replaceAll("\\s", "");
So you need to replace this char \0 with nothing:
resultat.replaceAll("\0", "");
or simply compare the reference string a to stringBuffer.toString() which is numCharsRead length:
if(a.equals(stringBuffer.toString())){System.out.println("ok");}
else System.out.println("not ok");

Reverse a string without using string functions [duplicate]

This question already has answers here:
Printing reverse of any String without using any predefined function?
(34 answers)
Closed 9 years ago.
How to write a java program to reverse a string without using string functions?
String a="Siva";
for(int i=0;i<=a.length()-1;i++)
{
System.out.print(a.charAt(i));
}
System.out.println("");
for(int i = a.length() - 1; i >= 0; --i)
{
System.out.print(a.charAt(i));
}
here charAt() and a.length() are string functions

This will help
public class StringReverse {
public static void main(String[] args){
String str = "Reverse";
StringBuilder sb = new StringBuilder(str);
str = sb.reverse().toString();
System.out.println("ReverseString : "+str);
}
}
There is no usage of String methods

String s = "abcdef";
char c[] = s.toCharArray();
for( int i = c.length -1; i>=0; i--)
System.out.print(c[i]);

Use StringBuilder class or StringBuffer class they have already a method reverse() for reversing the string
StringBuilder str = new StringBuilder("india");
System.out.println("string = " + str);
// reverse characters of the StringBuilder and prints it
System.out.println("reverse = " + str.reverse());
// reverse is equivalent to the actual
str = new StringBuilder("malayalam");
System.out.println("string = " + str);
// reverse characters of the StringBuilder and prints it
System.out.println("reverse = " + str.reverse());
http://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html

Below is ugly hack. It concept but it not invoke any String methods.
import java.io.*;
import java.util.*;
public class Hello {
public static String reverceWithoutStringMethods(String word){
String result = "";
//------ Write string to file -----------
BufferedWriter writer = null;
try {
writer = new BufferedWriter( new FileWriter("tempfile"));
writer.write(word);
}
catch ( IOException e) {}
finally {
try{
if ( writer != null) writer.close( );
}
catch ( IOException e){}
}
//------ read string from file -------------
RandomAccessFile f=null;
try {
f = new RandomAccessFile("tempfile", "r"); // Open file
int length = (int) f.length(); // Get length
// Read file
byte[] data = new byte[length];
f.readFully(data);
// Reverse data
for (int i=data.length; i>=0; i--){
result += (char)data[i-1];
}
} catch(Exception e){}
finally {
try{
f.close();
}
catch (Exception e){}
}
return result;
}
public static void main(String[] args) {
System.out.println(reverceWithoutStringMethods("Test"));
System.out.println(reverceWithoutStringMethods(""));
}
}
Output:
tseT

very long string as a response of web service

I am getting a really long string as the response of the web service I am collecting it in the using the StringBuilder but I am unable to obtain the full value I also used StringBuffer but had no success.
Here is the code I am using:
private static String read(InputStream in ) throws IOException {
//StringBuilder sb = new StringBuilder(1000);
StringBuffer sb = new StringBuffer();
String s = "";
BufferedReader r = new BufferedReader(new InputStreamReader( in ), 1000);
for (String line = r.readLine(); line != null; line = r.readLine()) {
sb.append(line);
s += line;
} in .close();
System.out.println("Response from Input Stream Reader >>>" + sb.toString());
System.out.println("Response from Input S >>>>>>>>>>>>" + s);
return sb.toString();
}
Any help is appreciated.

You can also split the string in array of strings in order to see all of them
String delimiter = "put a delimiter here e.g.: \n";
String[] datas=sb.toString().split(delimiter);
for(String string datas){
System.out.println("Response from Input S >>>>>>>>>>>>" + string);
}

The String may not print entirely to the console, but it is actually there. Save it to a file in order to see it.

I do not think that your input is too big for a String, but only not shown to the console because it doesn't accept too long lines. Anyways, here is the solution for a really huge input as characters:
private static String[] readHugeStream(InputStream in) throws IOException {
LinkedList<String> dataList = new LinkedList<>();
boolean finished = false;
//
BufferedReader r = new BufferedReader(new InputStreamReader(in), 0xFFFFFF);
String line = r.readLine();
while (!finished) {
int lengthRead = 0;
StringBuilder sb = new StringBuilder();
while (!finished) {
line = r.readLine();
if (line == null) {
finished = true;
} else {
lengthRead += line.length();
if (lengthRead == Integer.MAX_VALUE) {
break;
}
sb.append(line);
}
}
if (sb.length() != 0) {
dataList.add(sb.toString());
}
}
in.close();
String[] data = dataList.toArray(new String[]{});
///
return data;
}
public static void main(String[] args) {
try {
String[] data = readHugeStream(new FileInputStream("<big file>"));
} catch (IOException ex) {
Logger.getLogger(StackoverflowStringLong.class.getName()).log(Level.SEVERE, null, ex);
} catch (OutOfMemoryError ex) {
System.out.println("out of memory...");
}
}

System.out.println() does not print all the characters , it can display only limited number of characters in console. You can create a file in SD card and copy the string there as a text document to check your exact response.
try
{
File root = new File(Environment.getExternalStorageDirectory(), "Responsefromserver");
if (!root.exists())
{
root.mkdirs();
}
File gpxfile = new File(root, "response.txt");
FileWriter writer = new FileWriter(gpxfile);
writer.append(totalResponse);
writer.flush();
writer.close();
}
catch(IOException e)
{
System.out.println("Error:::::::::::::"+e.getMessage());
throw e;
}