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    <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&lt;String, Integer&gt; map = new HashMap&lt;String, Integer&gt;(); for (String arg : args) { String[] split = arg.split(Pattern.quote("=")); if (split.length &gt; 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&lt;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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    1. COI've never seen (String arg : args) before. Are the arg and args supposed to be variables? And the method put is supposed to print the result?
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    2. COSee my updated answer.
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    3. COSorry for asking alot of questions, but can you explain to me what the value of the split array is supposed to do? Is it supposed to combine the first two indexes and put the "=" between them?
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