Whenever I start a new project in Java I always find myself in need of some basic utility methods that are lacking in the standard library. I suppose that every programmer has his own little “bag of tricks” for every language (well, maybe not for python.. ❤ ).. and this is mine!
These are only some of the methods I use the most, of course, those that may be useful for many people 🙂
/*
* This program is free software. It comes without any warranty, to
* the extent permitted by applicable law. You can redistribute it
* and/or modify it under the terms of the Do What The Fuck You Want
* To Public License, Version 2, as published by Sam Hocevar. See
* http://sam.zoy.org/wtfpl/COPYING for more details.
*/
import java.util.List;
import java.util.Set;
/**
* Contains only a bunch of <code>static</code> utility methods.
*
* @author mb - somethingididnotknow.wordpress.com
*/
public final class Utilities {
/**
* Checks whether <strong>all</strong> the provided objects are
* <code>null</code>.
*
* @param objects
* a number of objects of any kind that are to be checked
* against <code>null</code>
* @return <code>true</code> in case <strong>all</strong> the argument
* objects are <code>null</code>, <code>false</code> otherwise.
*/
public static boolean areAllNull(Object... objects) {
for (Object o : objects) {
if (o != null)
return false;
}
return true;
}
/**
* Checks whether <strong>any</strong> of the argument objects is
* <code>null</code>.
*
* @param objects
* a number of objects of any kind that are to be checked
* against <code>null</code>.
* @return <code>true</code> if at least one of the arguments is
* <code>null</code>.
*/
public static boolean isAnyNull(Object... objects) {
for (Object o : objects) {
if (o == null)
return true;
}
return false;
}
/**
* Checks whether the two arguments are equal using a <em>null-safe</em>
* comparison.
*
* In case only one of the two objects is <code>null</code>,
* <code>false</code> is returned. In case both are not <code>null</code>
* {@link Object#equals(Object)} is called on the first object using the
* second as argument.
*
* @param first
* the first object to be checked.
* @param second
* the second object to be checked.
* @return <code>true</code> in case {@link Object#equals(Object)} returns
* <code>true</code> or the objects are both <code>null</code>,
* <code>false</code> otherwise.
*/
public static boolean nsEquals(Object first, Object second) {
if (first == null)
return second == null;
if (second == null)
return false;
return first.equals(second);
}
/**
* Returns a String that is empty in case the argument <tt>string</tt> is
* <code>null</code>, the unmodified <tt>string</tt> otherwise.
*
* @param string
* the string to be checked against <code>null</code>
* @return the empty String if <tt>string</tt> is <code>null</code>, the
* argument <tt>string</tt> unmodified otherwise
*/
public static String nonNull(final String string) {
return string == null ? "" : string;
}
/**
* An equivalent of Python's <code>str.join()</code> function on lists: it
* returns a String which is the concatenation of the strings in the
* argument array. The separator between elements is the argument
* <tt>toJoin</tt> string. The separator is only inserted between
* elements: there's no separator before the first element or after the
* last.
*
* @param toJoin
* the separator, if <code>null</code> the empty String is used
* @param list
* a list of <code>Object</code>s on which
* {@link Object#toString()} will be called
* @return the concatenation of String representations of the objects in
* the list
*/
public static String join(String toJoin, Object[] list) {
if (list == null || list.length == 0)
return "";
StringBuilder builder = new StringBuilder();
String delimiter = nonNull(toJoin);
int i = 0;
for (; i < (list.length - 1); i++) {
if (list[i] != null)
builder.append(list[i]);
builder.append(delimiter);
}
builder.append(list[i]);
return builder.toString();
}
/**
* An equivalent of Python's <code>str.join()</code> function on lists: it
* returns a String which is the concatenation of the strings in the
* argument list. The separator between elements is the string providing
* this method. The separator is only inserted between elements: there's
* no separator before the first element or after the last.
*
* @param toJoin
* the separator, if <code>null</code> the empty String is used
* @param list
* a list of <code>Object</code>s on which
* {@link Object#toString()} will be called
* @return the concatenation of String representations of the objects in
* the list
*/
public static String join(String toJoin, List list) {
if (list == null || list.isEmpty())
return "";
StringBuilder builder = new StringBuilder();
String delimiter = nonNull(toJoin);
int i = 0;
for (; i < list.size() - 1; i++) {
if (list.get(i) != null)
builder.append(list.get(i));
builder.append(delimiter);
}
builder.append(list.get(i));
return builder.toString();
}
/**
* An equivalent of Python's <code>str.join()</code> function on lists: it
* returns a String which is the concatenation of the strings in the
* argument list. The separator between elements is the string providing
* this method. The separator is only inserted between elements: there's
* no separator before the first element or after the last.
*
* @param toJoin
* the separator, if <code>null</code> the empty String is used
* @param set
* a set of <code>Object</code>s on which
* {@link Object#toString()} will be called
* @return the concatenation of String representations of the objects in
* the set
*/
public static String join(String toJoin, Set set) {
return join(toJoin, set.toArray());
}
/**
* Checks whether the argument <tt>array</tt> contains at least a
* <code>null</code> value.
*
* @param array
* the array to be checked.
* @return <code>true</code> in case <em>at least</em> one of the values
* stored in the argument <tt>array</tt> is <code>null</code>, or
* in case the <tt>array</tt> itself is <code>null</code>.
*/
public static boolean containsNull(Object[] array) {
if (array == null)
return true;
for (Object o : array) {
if (o == null)
return true;
}
return false;
}
/**
* Checks whether the argument <tt>list</tt> contains at least a
* <code>null</code> value.
*
* @param list
* the list to be checked
* @return <code>true</code> in case <em>at least</em> one of the values
* stored in the argument <tt>array</tt> is <code>null</code>, or
* in case the <tt>list</tt> itself is <code>null</code>
*/
public static boolean containsNull(List list) {
if (list == null)
return true;
for (Object o : list) {
if (o == null)
return true;
}
return false;
}
/**
* Checks whether the argument <tt>string</tt> is <code>null</code> or
* empty. Please note that the <tt>string</tt> is
* <strong>trimmed</strong>, so that a check on a string containing
* white spaces only will always return <code>true</code>.
*
* @param string
* the string to be checked
* @return <code>true</code> in case the argument <tt>string</tt> is
* <code>null</code>, empty ({@link String#length()} returns 0) or
* contains only white spaces (
* <tt>{@link String#trim()}.length()</tt> returns 0)
*/
public static boolean isNullOrEmpty(String string) {
return string == null || string.trim().length() == 0;
}
}
I don’t know what’s wrong with the syntax highlighter… here’s the same class in pastebin!
something I did not know 
[…] the spirit of my previous post on some of my favorite Java utility methods, I’ll post here this class, hoping that some of […]
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Hi there, I enjoy reading through your post. I wanted to write a little comment to support
you.
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hi! thanks! 🙂
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