Java Utililty Methods File Extension Name Get

String ext = null;
int k = fileName.lastIndexOf(EXTENSION_SEPARATOR); 
if (k != -1) {
    ext = fileName.substring(k + 1, fileName.length());
return ext;

int posExt = fileName.lastIndexOf(".");
return posExt == -1 ? "" : fileName.substring(posExt + 1);

fileName = new File(fileName).getName();
int dotIndex = fileName.lastIndexOf('.');
if (dotIndex == -1) {
    return "";
return fileName.substring(dotIndex + 1);

File f = new File(filePath);
String name = f.getName();
int pos = name.lastIndexOf('.');
if (pos >= 0 && pos < name.length() - 1) {
    return name.substring(pos + 1);
} else {
    return "";

if (filePath == null || filePath.trim().length() == 0) {
    return filePath;
int extenPosi = filePath.lastIndexOf(".");
int filePosi = filePath.lastIndexOf(File.separator);
if (extenPosi == -1) {
    return "";
return (filePosi >= extenPosi) ? "" : filePath.substring(extenPosi + 1);

String extension = "";
String fn = new File(filePath).getName();
if (fn.contains(".")) {
    String ext = filePath.substring(filePath.lastIndexOf(".") + 1).toLowerCase().trim();
    try {
        extension = ext;
    } catch (IllegalArgumentException e) {
return extension;

for (int i = fname.length() - 1; i >= 0; i--) {
    if ((fname.charAt(i) == '.') && (i != fname.length() - 1)) {
        return fname.substring(i + 1);
    if (fname.charAt(i) == File.separatorChar) {
        return "";
return "";

int iIndex = name.lastIndexOf('.');
if (iIndex >= 0) {
    return name.substring(iIndex);
return null;

String extension = "";
if (path != null && path.length() > 0) {
    int idx = path.lastIndexOf('.');
    if (idx >= 0) {
        int lastSlashIdx = path.lastIndexOf(java.io.File.separatorChar);
        if (idx > lastSlashIdx) {
            extension = path.substring(idx + 1);
return extension;