Merge pull request #311 from jentfoo/StringBuilder_tests

Adding a couple simple tests around the StringBuilder

test/StringBuilderTest.java

@@ -0,0 +1,65 @@
+
+public class StringBuilderTest {
+  private static final int iterations = 1000;
+    
+  public static void main(String[] args) {
+    verifyAppendStrLength();
+    verifyAppendCharLength();
+    verifySubstring();
+  }
+  
+  private static void verify(String srcStr, int iterations, String result) {
+    int expectedLength = srcStr.length() * iterations;
+    if (result.length() != expectedLength) {
+      throw new IllegalStateException("Incorrect length: " + result.length() + " vs " + expectedLength);
+    }
+  }
+  
+  private static void verify(String expected, String actual) {
+    if (! expected.equals(actual)) {
+      throw new IllegalStateException("Strings don't match, expected: " + expected + ", actual: " + actual);
+    }
+  }
+  
+  private static void verifyAppendStrLength() {
+    String fooStr = "foobar";
+    
+    StringBuilder sb = new StringBuilder();
+    for (int i = 0; i < iterations; i++) {
+      sb.append(fooStr);
+    }
+    String result = sb.toString();
+    
+    verify(fooStr, iterations, result);
+  }
+  
+  private static void verifyAppendCharLength() {
+    int iterations = 5000;
+    String fooStr = "foobar";
+    char[] fooChars = new char[fooStr.length()];
+    fooStr.getChars(0, fooStr.length(), fooChars, 0);
+    
+    StringBuilder sb = new StringBuilder();
+    for (int i = 0; i < iterations; i++) {
+      for (int j = 0; j < fooChars.length; j++) {
+        sb.append(fooChars[j]);
+      }
+    }
+    String result = sb.toString();
+    
+    verify(fooStr, iterations, result);
+  }
+  
+  private static void verifySubstring() {
+    String fooStr = "foobar";
+    StringBuilder sb = new StringBuilder();
+    sb.append(fooStr);
+    sb.append(fooStr);
+    
+    String beginingSubString = sb.substring(0, fooStr.length());
+    verify(fooStr, beginingSubString);
+    
+    String endSubString = sb.substring(fooStr.length());
+    verify(fooStr, endSubString);
+  }
+}