title: String.contains in Java
body: <pre><code>String s1 = "The quick brown fox jumps over the lazy dog";
  String s2 = "";
  boolean b = s1.contains(s2);
  System.out.println(b);
  </code></pre>
  
  <p>I run the Java code above, the b return true.
  Since s2 is empty, why does s1 contains s2?</p>
  
  <p>I check the Java API, it write:</p>
  
  <p>Returns true if and only if this string contains the specified sequence of char values. </p>
  
  <p>Parameters:</p>
  
  <p>s - the sequence to search for </p>
  
  <p>Returns:</p>
  
  <p>true if this string contains s, false otherwise</p>