StringUtils: add splitUnquoted method

This lets you split on a separator string but ignore instances
of it inside of quotations ("). Does not support escaped quotes.

Author: ctrueden

src/main/java/org/scijava/util/StringUtils.java

@@ -63,6 +63,7 @@
 
 import java.io.File;
 import java.text.DecimalFormatSymbols;
+import java.util.regex.Pattern;
 
 /**
  * Useful methods for working with {@link String}s.
@@ -80,6 +81,16 @@ private StringUtils() {
 		// NB: prevent instantiation of utility class.
 	}
 
+	/**
+	 * Splits a string only at separators outside of quotation marks ({@code "}).
+	 * Does not handle escaped quotes.
+	 */
+	public static String[] splitUnquoted(final String s, final String separator) {
+		// See https://stackoverflow.com/a/1757107/1919049
+		return s.split(Pattern.quote(separator) +
+			"(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)", -1);
+	}
+
 	/** Normalizes the decimal separator for the user's locale. */
 	public static String sanitizeDouble(String value) {
 		value = value.replaceAll("[^0-9,\\.]", "");

src/test/java/org/scijava/util/StringUtilsTest.java

@@ -32,6 +32,7 @@
 
 package org.scijava.util;
 
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -47,6 +48,21 @@
  */
 public class StringUtilsTest {
 
+	/** Tests {@link StringUtils#splitUnquoted}. */
+	@Test
+	public void testSplitUnquoted() {
+		// See https://stackoverflow.com/a/1757107/1919049
+		final String line = "foo,bar,c;qual=\"baz,blurb\",d;junk=\"quux,syzygy\"";
+		final String[] expected = {
+			"foo",
+			"bar",
+			"c;qual=\"baz,blurb\"",
+			"d;junk=\"quux,syzygy\""
+		};
+		final String[] actual = StringUtils.splitUnquoted(line, ",");
+		assertArrayEquals(expected, actual);
+	}
+
 	@Test
 	public void isNullOrEmptyFalseIfString() throws Exception {
 		assertFalse(StringUtils.isNullOrEmpty("Fresh out of Red Leicester"));