Search for keyword in the given context

build.xml

@@ -82,4 +82,10 @@
       <classpath refid="classpath.examples"/>
     </java>
   </target>
+
+  <target name="run-kwik-example" depends="examples-compile">
+    <java classname="KWIK">
+      <classpath refid="classpath.examples"/>
+    </java>
+  </target>
 </project>

examples/KWIK.java

@@ -0,0 +1,68 @@
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+/**
+ * Keyword-in-context search.
+ *
+ * Computes all of the occurrences of a keyword in a string, with surrounding
+ * context.
+ */
+public class KWIK {
+
+  /**
+   * Reads the contents of the specified file and returns them as a string.
+   *
+   * @param filePath the path to the input file
+   */
+  private static String readFileAsString(String filePath) {
+    File f = new File(filePath);
+    BufferedReader reader = null;
+    StringBuilder text = new StringBuilder();
+    String line = null;
+
+    try {
+      reader = new BufferedReader(new FileReader(f));
+      while ((line = reader.readLine()) != null) {
+        text.append(line);
+      }
+    } catch (FileNotFoundException e) {
+      e.printStackTrace();
+    } catch (IOException e) {
+      e.printStackTrace();
+    } finally {
+      try {
+        if (reader != null) {
+          reader.close();
+        }
+      } catch (IOException e) {
+      }
+    }
+
+    return text.toString();
+  }
+
+  public static void main(String[] args) {
+    String text = readFileAsString("./data/brave_new_world.txt");
+    // int context = Integer.parseInt(args[0]);
+    // String query = args[1];
+
+    // number of characters of surrounding context in each side
+    int context = 20;
+
+    // query string
+    String query = "world";
+
+    int length = text.length();
+
+    // build suffix array
+    SuffixArray sa = new SuffixArray(text);
+
+    for (int i = sa.rank(query); i < length && sa.selectAsString(i).startsWith(query); i++) {
+      int from = Math.max(0, sa.indexOf(i) - context);
+      int to   = Math.min(length-1, from + query.length() + 2*context);
+      System.out.println(text.substring(from, to));
+    }
+  }
+}

examples/README.md

@@ -16,5 +16,6 @@ Here's the complete list of available examples.
   * `ant run-suffixArray-example`
   * `ant run-lrs-example`
   * `ant run-lcs-example`
+  * `ant run-kwik-example`
 
 *Note: a better approach for running the examples is yet to be determined.*