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copied!<p>A good place to start would be a <a href="http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html" rel="nofollow">HashMap</a> and <a href="http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split%28java.lang.String%29" rel="nofollow">String.split</a>.</p> <p>You might try something like this:</p> <pre><code>// In main function HashMap<String, Integer> map = new HashMap<String, Integer>(); for (String arg : args) { String[] split = arg.split(Pattern.quote("=")); if (split.length > 1) { // It had an equals sign. String var = split[0], value = split[1]; map.put(var, Integer.parseInt(value)); System.out.println(var + " is now " + value); } } </code></pre> <p>This won't account for <code>A+B</code>, but I'll leave that as a puzzle to you.</p> <p><em>Hint</em>: <a href="http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html#containsKey%28java.lang.Object%29" rel="nofollow">map.containsKey</a>, <a href="http://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html#get%28java.lang.Object%29" rel="nofollow">map.get</a>.</p> <hr> <p><strong>EDIT</strong></p> <p>To answer your questions:</p> <pre><code>for (int i=0; i<args.length; i++) { String arg = args[i]; // do something with arg } </code></pre> <p>is the same as </p> <pre><code>for (String arg : args) { // do something with arg } </code></pre> <p>The latter is called "for-each" or "for-in." The <code>args</code> variable contains the command-line arguments. I'm assuming that this code is in the main method, which should have a method signature of <code>public static void main(</code><strong><code>String[] args</code></strong><code>)</code>.</p> <p>The <code>put</code> method adds the key/value pair to the HashMap. Basically, a hashmap is an association (map) of keys to values. Each key can have one value, and <code>put</code> overwrites, so if you run</p> <pre><code>map.put("a", 1); map.put("b", 2); map.put("a", 3); </code></pre> <p>then the following statements are true:</p> <pre><code>map.get("a") == 3 map.get("b") == 2 map.get("c") == null map.get("asdf") == null </code></pre> <p>For more info, check out the <a href="http://docs.oracle.com/javase/tutorial/collections/interfaces/map.html" rel="nofollow">map tutorial</a>.</p>

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