Java Utililty Methods File Delete

boolean success = f.delete();
String path = f.getAbsolutePath();
if (success) {
    System.out.println("delete file : " + path);
} else {
    throw new IllegalStateException("deleting file failed. " + path);

if (f.isDirectory() && f.listFiles() != null) {
    final File[] files = f.exists() && f.listFiles() == null ? new File[0] : f.listFiles();
    assert files != null;
    for (File c : files)
        delete(c);
if (!f.delete()) {
    throw new IOException("Failed to delete file: " + f);
...

if (f != null) {
    if (f.isFile()) {
        f.delete();
    } else {
        File[] files = f.listFiles();
        if (files != null) {
            for (int i = 0; i < files.length; i++) {
                File current = files[i];
...

if (!f.exists())
    throw new IllegalArgumentException("Delete: no such file or directory: " + f.getName());
boolean success = f.delete();
if (!success)
    throw new IllegalArgumentException("Delete: deletion failed: " + f.getAbsolutePath());

try {
    if (f.exists()) {
        if (f.isDirectory()) {
            File[] child = f.listFiles();
            for (File fc : child) {
                delete(fc);
        f.delete();
    f.deleteOnExit();
} catch (Exception e) {
    e.printStackTrace();
    throw e;

boolean isDeleted = f.delete();
for (int i = 0; i < 4 && !isDeleted; i++) {
    try {
        Thread.sleep(1000);
    } catch (InterruptedException e) {
        throw new IOException("Failed to delete file: " + f, e);
    isDeleted = f.delete();
...

if (f == null)
    return true;
if (f.isDirectory()) {
    File[] cf = f.listFiles();
    if (cf != null)
        for (File c : cf)
            delete(c);
return f.delete();

delete_(f, false);

if (f != null) {
    if (f.isDirectory()) {
        for (File child : f.listFiles()) {
            delete(child);
        return f.delete();
    } else {
        return f.delete();
...

boolean deleted = false;
if (f.exists()) {
    if (f.isFile()) {
        deleted = f.delete();
    } else {
        File[] subs = f.listFiles();
        if (subs != null && subs.length > 0) {
            for (int i = 0; i < subs.length; i++) {
...