title: What does "zero-extend" mean?
body: <p>I was looking at the <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/CharSequence.html" rel="noreferrer">Javadoc for the CharSequence</a> interface, implemented by <code>String</code>, <code>StringBufer</code>and a few others, more specifically at the <code>chars()</code> method, and the Javadoc says</p>
  
  <blockquote>
    <p>Returns a stream of int zero-extending the char values from this
    sequence.</p>
  </blockquote>
  
  <p>Now, I know that it returns <code>int</code> values, and that <a href="https://stackoverflow.com/questions/17984975/convert-int-to-char-in-java"><code>int</code> that can be cast to <code>char</code></a>. But what does "zero-extending" mean?</p>