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POFind a char optimization
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  1. POFind a char optimization
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    copied!<p>So this part of the homework wants us to take a Set of Strings and we will return a List of Strings. In the String Set we will have email addresses ie myname@uark.edu. We are to pull the first part of the email address; the name and put it in the String List.From the above example myname would be put into the List. The code I currently have uses an iterator to pull a string from the Set. I then use the String.contains("@") as an error check to make sure the String has an @ symbol in it. I then start at the end of the string and use the string.charAt("@") to check each char. Once It's found i then make a substring with the correct part and send it to the List. My problem is i wanted to use something recursive and cut down on operations. I was thinking of something that would divide the string.length()/2 and then use String.contains("@") on the second half first. If that half does contain the @ symbol then it would call the functions recursively agin. If the back half did not contain the @ symbol then the front half would have it and we would call the function recursively sending it. </p> <p>So my problem is when I call the function recursively and send it the "substring" once I find the @ symbol I will only have the index of the substring and not the index of the original string. Any ideas on how to keep track of it or maybe a command/method I should be looking at. Below is my original code. Any advice welcome.</p> <pre><code>public static List&lt;String&gt; parseEmail(Set&lt;String&gt; emails) { List&lt;String&gt; _names = new LinkedList&lt;String&gt;(); Iterator&lt;String&gt; eMailIt=emails.iterator(); while(eMailIt.hasNext()) { String address=new String(eMailIt.next()); boolean check=true; if(address.contains("@"))//if else will catch addresses that do not contain '@' . { String _address=""; for(int i=address.length(); i&gt;0 &amp;&amp; check; i--) { if('@'==address.charAt(i-1)) { _address=new String(address.substring(0,i-1)); check=false; } } _names.add(_address); //System.out.println(_address);//fill in with correct sub string } else { //System.out.println("Invalid address"); _names.add("Invalid address");//This is whats shownn when you have an address that does not have an @ in it. } // could have it insert some other char i.e. *%# s.t. if you use the returned list it can skip over invalid emails } return _names; } </code></pre> <p>**It was suggested I use the String.indexOf("@") BUT according to the API this method only gives back the first occurrence of the symbol and I have to work on the assumption that there could be multiple "@" in the address and I have to use the last one. Thank you for the suggestion though. Am looking at the other suggestion and will report back. </p> <p>***So there is a string.lastindexOf() and that was what I needed. </p> <pre><code>public static List&lt;String&gt; parseEmail(Set&lt;String&gt; emails) { List&lt;String&gt; _names = new LinkedList&lt;String&gt;(); Iterator&lt;String&gt; eMailIt=emails.iterator(); while(eMailIt.hasNext()) { String address=new String(eMailIt.next()); if(address.contains("@"))//if else will catch addresses that do not contain '@' . { int endex=address.lastIndexOf('@'); _names.add(address.substring(0,endex-1)); // System.out.println(address.substring(0,endex)); } else { // System.out.println("Invalid address"); _names.add("Invalid address");//This is whats shownn when you have an address that does not have an @ in it. } // could have it insert some other char i.e. *%# s.t. if you use the returned list it can skip over invalid emails } return _names; } </code></pre>
 

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