What is the best approach to parse a String type to other numeric types available in Java?
<p>Let's consider the following code snippet in Java. There are some of possible approaches (that I know) to parse a String value to other numeric types (Let's say for the sake of simplicity, it is an Integer, a wrapper type in Java).</p>

<pre><code>package parsing;

final public class Parsing
{
    public static void main(String[] args)
    {
        String s="100";

        Integer temp=new Integer(s);
        System.out.print("\ntemp = "+temp);

        temp=Integer.parseInt(s);
        System.out.print("\ntemp = "+temp);        

        temp=Integer.valueOf(s).intValue();
        System.out.print("\ntemp = "+temp);

        temp=Integer.getInteger(s);
        System.out.print("\ntemp = "+temp);
    }    
}
</code></pre>

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<p>In all the cases except the last one, returns the value 100 after converting it into an Integer. Which one is the best approach to parse a String value to other numeric types available in Java? The last case returns NULL even if the String object <strong>s</strong> already contains a parsable value. Why?</p>
