Add LibUsbException for easier error code handling

src/main/java/org/usb4java/LibUsbException.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2014 Klaus Reimer <k@ailis.de>
+ * See LICENSE.md for licensing information.
+ */
+
+package org.usb4java;
+
+/**
+ * A runtime exception which automatically outputs the libusb error string.
+ *
+ * @author Klaus Reimer (k@ailis.de)
+ */
+public final class LibUsbException extends RuntimeException
+{
+    /** Serial version UID. */
+    private static final long serialVersionUID = 1L;
+
+    /** The libusb error code. */
+    private final int errorCode;
+    
+    /**
+     * Constructs a libusb exception which just outputs the error code and
+     * the error message from libusb.
+     *
+     * @param errorCode
+     *            The error code.
+     */
+    public LibUsbException(final int errorCode)
+    {
+        super(String.format("USB error %d: %s", -errorCode,
+            LibUsb.strError(errorCode)));
+        this.errorCode = errorCode;
+    }
+
+    /**
+     * Constructs a libusb exception which outputs the error code and
+     * the error message from libusb together with a custom error message.
+     *
+     * @param message
+     *            The error message.
+     * @param errorCode
+     *            The error code.
+     */
+    public LibUsbException(final String message, final int errorCode)
+    {
+        super(String.format("USB error %d: %s: %s", -errorCode, message,
+            LibUsb.strError(errorCode)));
+        this.errorCode = errorCode;
+    }
+
+    /**
+     * Returns the error code.
+     *
+     * @return The error code
+     */
+    public int getErrorCode()
+    {
+        return this.errorCode;
+    }    
+}