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Java Client Core Library for Keen
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package io.keen.client.java;

import java.io.Closeable;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Scanner;

/**
 * KeenUtils
 *
 * @author dkador
 * @since 1.0.0
 */
public class KeenUtils {

    private final static char[] hexArray = {'0', '1', '2', '3', '4', '5', '6', '7',
            '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

    public static void closeQuietly(Closeable c) {
        if (c != null) {
            try {
                c.close();
            } catch (IOException e) {
                // Ignore.
            }
        }
    }

    public static String convertFileToString(java.io.File file) throws IOException {
        Scanner s = new Scanner(file, "UTF-8").useDelimiter("\\A");
        String result =  s.hasNext() ? s.next() : "";
        s.close();
        return result;
    }

    public static String convertStreamToString(java.io.InputStream is) {
        Scanner s = new Scanner(is).useDelimiter("\\A");
        return s.hasNext() ? s.next() : "";
    }

    public static String getStackTraceFromThrowable(Throwable t) {
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw);
        t.printStackTrace(pw);
        return sw.toString(); // stack trace as a string
    }

    public static byte[] hexStringToByteArray(String s) {
        int len = s.length();
        if (len % 2 != 0) {
            throw new IllegalArgumentException("Hex string must have an even length");
        }

        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) +
                    Character.digit(s.charAt(i + 1), 16));
        }

        return data;
    }

    public static String byteArrayToHexString(byte[] bytes) {
        char[] hexChars = new char[bytes.length * 2];

        for (int i = 0; i < bytes.length; i++) {
            int b = bytes[i] & 0xFF;
            hexChars[i * 2] = hexArray[b >>> 4];
            hexChars[(i * 2) + 1] = hexArray[b & 0x0F];
        }

        return new String(hexChars);
    }
}