title: What does a[c - 'a' ]++ mean in Java?
body: <p>The goal is to count the common characters in two strings and return an integer. I understand everything except</p>
  <pre><code>a[c - 'a' ]++;
  </code></pre>
  <p>I've tried searching through a few classes's documentation, googling whats in quotations, and googling a few possible descriptions for what is happening, but I am unable to even find out what to call <code>a[c - 'a' ]++;</code> let alone what it's actually doing. To me it seems it's counting an occurrence of a particular char but I am uncertain.</p>
  <p>Here's the code</p>
  <pre><code>int commonCharacterCount(String s1, String s2) {
  int[] a = new int[26], 
      b = new int[26];
  for (char c: s1.toCharArray())
      a[c - 'a']++;
  for (char c: s2.toCharArray())
      b[c - 'a']++;
  int s = 0;
  for (int i = 0; i &lt; 26; ++i) 
      s +=Math.min(a[i],b[i]);
  return s;
  </code></pre>