naturalCompare for sorting in "natural/human" sort order

platform/util/src/com/intellij/openapi/util/text/StringUtil.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2010 JetBrains s.r.o.
+ * Copyright 2000-2011 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -1959,6 +1959,58 @@ public class StringUtil {
     return res;
   }
 
+  /**
+   * Implementation of "Sorting for Humans: Natural Sort Order":
+   * http://www.codinghorror.com/blog/2007/12/sorting-for-humans-natural-sort-order.html
+   */
+  public static int naturalCompare(String string1, String string2) {
+    return naturalCompare(string1, string2, false);
+  }
+
+  private static int naturalCompare(String string1, String string2, boolean caseSensitive) {
+    final int string1Length = string1.length();
+    final int string2Length = string2.length();
+    for(int i = 0, j = 0; i < string1Length && j < string2Length; i++, j++) {
+      final char ch1 = string1.charAt(i);
+      final char ch2 = string2.charAt(j);
+      if (isDigit(ch1) && isDigit(ch2)) {
+        int startNum1 = i;
+        int startNum2 = j;
+        i++;
+        j++;
+        while (i < string1Length && isDigit(string1.charAt(i))) i++;
+        while (j < string2Length && isDigit(string2.charAt(j))) j++;
+        final int difference = Integer.parseInt(string1.substring(startNum1, i)) -
+                               Integer.parseInt(string2.substring(startNum2, j));
+        if (difference != 0) {
+          return difference;
+        }
+      } else {
+        if (caseSensitive) {
+          return ch1 - ch2;
+        } else {
+          // similar logic to charsMatch() below
+          final int diff1 = Character.toUpperCase(ch1) - Character.toUpperCase(ch2);
+          if (diff1 != 0) {
+            final int diff2 = Character.toLowerCase(ch1) - Character.toLowerCase(ch2);
+            if (diff2 != 0) {
+              return diff1;
+            }
+          }
+        }
+      }
+    }
+    if (!caseSensitive && string1Length == string2Length) {
+      // do case sensitive compare if case insensitive strings are equal
+      return naturalCompare(string1, string2, true);
+    }
+    return string1Length - string2Length;
+  }
+
+  public static boolean isDigit(char c) {
+    return c >= '0' && c <= '9';
+  }
+
   public static int compare(@Nullable String s1, @Nullable String s2, boolean ignoreCase) {
     if (s1 == s2) return 0;
     if (s1 == null) return -1;

platform/util/testSrc/com/intellij/util/text/StringUtilTest.java

@@ -18,7 +18,7 @@ package com.intellij.util.text;
 import com.intellij.openapi.util.text.StringUtil;
 import junit.framework.TestCase;
 
-import java.util.List;
+import java.util.*;
 
 /**
  * @author Eugene Zhuravlev
@@ -70,4 +70,21 @@ public class StringUtilTest extends TestCase {
     assertFalse(StringUtil.startsWithConcatenationOf("something", "something", "."));
     assertFalse(StringUtil.startsWithConcatenationOf("some", "something", ""));
   }
+
+  public void testNaturalCompare() {
+    final List<String> strings = new ArrayList(Arrays.asList("Test99", "tes0", "test0", "testing", "test", "test99", "test011", "test1",
+                                                             "test 3", "test2", "test10a", "test10", "1.2.10.5", "1.2.9.1"));
+    final Comparator<String> c = new Comparator<String>() {
+      @Override
+      public int compare(String o1, String o2) {
+        return StringUtil.naturalCompare(o1, o2);
+      }
+    };
+    Collections.sort(strings, c);
+    assertEquals(Arrays.asList("1.2.9.1", "1.2.10.5", "tes0", "test", "test 3", "test0", "test1", "test2", "test10", "test10a",
+                               "test011", "Test99", "test99", "testing"), strings);
+    final List<String> strings2 = new ArrayList(Arrays.asList("t1", "T2", "T1", "t2"));
+    Collections.sort(strings2, c);
+    assertEquals(Arrays.asList("T1", "t1", "T2", "t2"), strings2);
+  }
 }