Replace "String.length()" == 0 with "String.isEmpty()".

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/io/trunk@1586504 13f79535-47bb-0310-9956-ffa450edef68

Author: garydgregory

src/main/java/org/apache/commons/io/ByteOrderMark.java

@@ -74,7 +74,7 @@ public class ByteOrderMark implements Serializable {
      * length
      */
     public ByteOrderMark(final String charsetName, final int... bytes) {
-        if (charsetName == null || charsetName.length() == 0) {
+        if (charsetName == null || charsetName.isEmpty()) {
             throw new IllegalArgumentException("No charsetName specified");
         }
         if (bytes == null || bytes.length == 0) {

src/main/java/org/apache/commons/io/FileSystemUtils.java

@@ -378,7 +378,7 @@ long parseDir(final String line, final String path) throws IOException {
      * @throws IOException if an error occurs
      */
     long freeSpaceUnix(final String path, final boolean kb, final boolean posix, final long timeout) throws IOException {
-        if (path.length() == 0) {
+        if (path.isEmpty()) {
             throw new IllegalArgumentException("Path must not be empty");
         }
 

src/main/java/org/apache/commons/io/FilenameUtils.java

@@ -1156,7 +1156,7 @@ public static boolean isExtension(final String filename, final String extension)
         if (filename == null) {
             return false;
         }
-        if (extension == null || extension.length() == 0) {
+        if (extension == null || extension.isEmpty()) {
             return indexOfExtension(filename) == NOT_FOUND;
         }
         final String fileExt = getExtension(filename);

src/main/java/org/apache/commons/io/filefilter/MagicNumberFileFilter.java

@@ -163,7 +163,7 @@ public MagicNumberFileFilter(final String magicNumber, final long offset) {
         if (magicNumber == null) {
             throw new IllegalArgumentException("The magic number cannot be null");
         }
-        if (magicNumber.length() == 0) {
+        if (magicNumber.isEmpty()) {
             throw new IllegalArgumentException("The magic number must contain at least one byte");
         }
         if (offset < 0) {