Applying Arnaud Brunet's patch from LANG-355 to make StrBuilder implement CharSequence

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/lang/trunk@795600 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/lang/text/StrBuilder.java

@@ -71,7 +71,7 @@
  * @since 2.2
  * @version $Id$
  */
-public class StrBuilder {
+public class StrBuilder implements CharSequence {
 
     /**
      * The extra capacity for new builders.
@@ -1917,6 +1917,22 @@ public boolean endsWith(String str) {
     }
 
     //-----------------------------------------------------------------------
+    /**
+     * {@inheritDoc}
+     */
+    public CharSequence subSequence(int startIndex, int endIndex) {
+      if (startIndex < 0) {
+          throw new StringIndexOutOfBoundsException(startIndex);
+      }
+      if (endIndex > size) {
+          throw new StringIndexOutOfBoundsException(endIndex);
+      }
+      if (startIndex > endIndex) {
+          throw new StringIndexOutOfBoundsException(endIndex - startIndex);
+      }
+      return substring(startIndex, endIndex);
+    }
+
     /**
      * Extracts a portion of this string builder as a string.
      * 

src/test/org/apache/commons/lang/text/StrBuilderTest.java

@@ -1099,6 +1099,39 @@ public void testEndsWith() {
     }
 
     //-----------------------------------------------------------------------
+    public void testSubSequenceIntInt() {
+       StrBuilder sb = new StrBuilder ("hello goodbye");
+       // Start index is negative
+       try {
+            sb.subSequence(-1, 5);
+            fail();
+        } catch (IndexOutOfBoundsException e) {}
+        
+        // End index is negative
+       try {
+            sb.subSequence(2, -1);
+            fail();
+        } catch (IndexOutOfBoundsException e) {}
+        
+        // End index greater than length()
+        try {
+            sb.subSequence(2, sb.length() + 1);
+            fail();
+        } catch (IndexOutOfBoundsException e) {}
+        
+        // Start index greater then end index
+        try {
+            sb.subSequence(3, 2);
+            fail();
+        } catch (IndexOutOfBoundsException e) {}
+        
+        // Normal cases
+        assertEquals ("hello", sb.subSequence(0, 5));
+        assertEquals ("hello goodbye".subSequence(0, 6), sb.subSequence(0, 6));
+        assertEquals ("goodbye", sb.subSequence(6, 13));
+        assertEquals ("hello goodbye".subSequence(6,13), sb.subSequence(6, 13));
+    }
+
     public void testSubstringInt() {
         StrBuilder sb = new StrBuilder ("hello goodbye");
         assertEquals ("goodbye", sb.substring(6));