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copied!<p>Let's go through it line by line.</p> <p><strong>Line 11</strong></p> <p>An easy start, no strings created here.</p> <p><strong>Line 12</strong></p> <p>We're assigning the String <code>"Fred"</code> to <code>s</code>. Although it looks like a String is created here, this string will live in the constant pool. The <a href="http://docs.oracle.com/javase/specs/jvms/se5.0/html/VMSpecTOC.doc.html" rel="nofollow">JVMS</a> section <a href="http://docs.oracle.com/javase/specs/jvms/se5.0/html/Concepts.doc.html#19124" rel="nofollow">2.17.6 Creation of New Class Instances</a> guarantees that the objects for string literals will <em>at latest</em> be created when the surrounding class is loaded, which by definition is <em>before the method is invoked</em>. So no new string objects are created on this line.</p> <p><strong>Line 13</strong></p> <p>The literal string <code>"47"</code> is referenced, which again will have been created statically (as above). However there's also the invocation of the <code>+</code> operator, which <em>will</em> create a new String in order to hold the result of the concatenation. So that's the first string created.</p> <p><strong>Line 14</strong></p> <p>The <code>substring</code> method does indeed create a new String. It shares the underlying character array with its parent - and so takes up hardly any extra memory - but since Strings are immutable, each different string representation requires a different <code>String</code> object. (This is probably a gotcha - my first instinctive response was "ah, string created by substring are special" but of course it still has to create a new object).</p> <p><strong>Line 15</strong></p> <p>As above - the uppercase representation is different, so a new String must be created to hold the result.</p> <p><strong>Line 16</strong></p> <p><code>Strings</code> override the <code>toString()</code> method to simply <code>return this</code> - hence no additional String is created.</p> <p><strong>The scores on the doors</strong></p> <p>By my count that's three String objects created during this method (with two of those objects sharing the same underlying character array, and with two pre-existing objects referenced for the string literals).</p>

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