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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.

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/*
 * #%L
 * SciJava Common shared library for SciJava software.
 * %%
 * Copyright (C) 2009 - 2017 Board of Regents of the University of
 * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
 * Institute of Molecular Cell Biology and Genetics.
 * %%
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// File path shortening code adapted from:
// from: http://www.rgagnon.com/javadetails/java-0661.html

package org.scijava.util;

import java.util.List;

/**
 * Useful methods for working with {@link List}s.
 * 
 * @author Curtis Rueden
 */
public final class ListUtils {

	private ListUtils() {
		// prevent instantiation of utility class
	}

	/** Gets the first element of the given list, or null if none. */
	public static  T first(final List list) {
		if (list == null || list.size() == 0) return null;
		return list.get(0);
	}

	/**
	 * Converts the given list to a string.
	 * 
	 * The list elements will be separated by a comma then a space. The list will
	 * be enclosed in square brackets.
	 * 
	 * 
	 * @param list The list to stringify.
	 * @see #string(List, String, String, String, boolean)
	 */
	public static String string(final List list) {
		return string(list, true);
	}

	/**
	 * Converts the given list to a string.
	 * 
	 * The list elements will be separated by a comma then a space. The list will
	 * be enclosed in square brackets unless it is a singleton with the
	 * {@code encloseSingletons} flag set to false.
	 * 
	 * 
	 * @param list The list to stringify.
	 * @param encloseSingletons Whether to enclose singleton lists in brackets.
	 * @return The stringified list.
	 * @see #string(List, String, String, String, boolean)
	 */
	public static String string(final List list,
		final boolean encloseSingletons)
	{
		return string(list, "[", "]", ", ", encloseSingletons);
	}

	/**
	 * Converts the given list to a string.
	 * 
	 * The list elements will be comma-separated. It will be enclosed in square
	 * brackets unless the list is a singleton with the {@code encloseSingletons}
	 * flag set to false.
	 * 
	 * 
	 * @param list The list to stringify.
	 * @param lDelimiter The left-hand symbol(s) in which to enclose the list.
	 * @param rDelimiter The right-hand symbol(s) in which to enclose the list.
	 * @param separator The symbol(s) to place in between each element.
	 * @param encloseSingletons Whether to enclose singleton lists inside the
	 *          delimiter symbols.
	 * @return The stringified list.
	 */
	public static String string(final List list, //
		final String lDelimiter, final String rDelimiter, //
		final String separator, final boolean encloseSingletons)
	{
		final boolean delimit = encloseSingletons || list.size() != 1;
		final StringBuilder sb = new StringBuilder();
		if (delimit) sb.append(lDelimiter);
		boolean first = true;
		for (final Object e : list) {
			if (first) first = false;
			else sb.append(separator);
			sb.append(e);
		}
		if (delimit) sb.append(rDelimiter);
		return sb.toString();
	}
}