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    <p><code>[Ljava.lang.Object;</code> is the name for <code>Object[].class</code>, the <a href="http://download.oracle.com/javase/6/docs/api/java/lang/Class.html" rel="noreferrer"><code>java.lang.Class</code></a> representing the class of array of <code>Object</code>.</p> <p>The naming scheme is documented in <a href="http://download.oracle.com/javase/6/docs/api/java/lang/Class.html#getName%28%29" rel="noreferrer"><code>Class.getName()</code></a>:</p> <blockquote> <p>If this class object represents a reference type that is not an array type then the binary name of the class is returned, as specified by the Java Language Specification (<a href="http://java.sun.com/docs/books/jls/third_edition/html/binaryComp.html#13.1" rel="noreferrer">§13.1</a>).</p> <p>If this class object represents a primitive type or <code>void</code>, then the name returned is the Java language keyword corresponding to the primitive type or <code>void</code>. </p> <p>If this class object represents a class of arrays, then the internal form of the name consists of the name of the element type preceded by one or more <code>'['</code> characters representing the depth of the array nesting. The encoding of element type names is as follows:</p> <pre><code>Element Type Encoding boolean Z byte B char C double D float F int I long J short S class or interface Lclassname; </code></pre> </blockquote> <p>Yours is the last on that list. Here are some examples:</p> <pre><code>// xxxxx varies System.out.println(new int[0][0][7]); // [[[I@xxxxx System.out.println(new String[4][2]); // [[Ljava.lang.String;@xxxxx System.out.println(new boolean[256]); // [Z@xxxxx </code></pre> <p>The reason why the <code>toString()</code> method on arrays returns <code>String</code> in this format is because arrays do not <code>@Override</code> the method inherited from <code>Object</code>, which is specified as follows:</p> <blockquote> <p>The <a href="http://download.oracle.com/javase/6/docs/api/java/lang/Object.html#toString%28%29" rel="noreferrer"><code>toString</code> method for class <code>Object</code></a> returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:</p> <pre><code> getClass().getName() + '@' + Integer.toHexString(hashCode()) </code></pre> </blockquote> <p><strong><em>Note</em></strong>: you can not rely on the <code>toString()</code> of any arbitrary object to follow the above specification, since they can (and usually do) <code>@Override</code> it to return something else. The more reliable way of inspecting the type of an arbitrary object is to invoke <a href="http://download.oracle.com/javase/6/docs/api/java/lang/Object.html#getClass%28%29" rel="noreferrer"><code>getClass()</code></a> on it (a <code>final</code> method inherited from <code>Object</code>) and then <a href="http://java.sun.com/developer/technicalArticles/ALT/Reflection/index.html" rel="noreferrer">reflecting</a> on the returned <code>Class</code> object. Ideally, though, the API should've been designed such that reflection is not necessary (see <em>Effective Java 2nd Edition, Item 53: Prefer interfaces to reflection</em>).</p> <hr> <h3>On a more "useful" <code>toString</code> for arrays</h3> <p><a href="http://download.oracle.com/javase/6/docs/api/java/util/Arrays.html" rel="noreferrer"><code>java.util.Arrays</code></a> provides <code>toString</code> overloads for primitive arrays and <code>Object[]</code>. There is also <code>deepToString</code> that you may want to use for nested arrays.</p> <p>Here are some examples:</p> <pre><code> int[] nums = { 1, 2, 3 }; System.out.println(nums); // [I@xxxxx System.out.println(Arrays.toString(nums)); // [1, 2, 3] int[][] table = { { 1, }, { 2, 3, }, { 4, 5, 6, }, }; System.out.println(Arrays.toString(table)); // [[I@xxxxx, [I@yyyyy, [I@zzzzz] System.out.println(Arrays.deepToString(table)); // [[1], [2, 3], [4, 5, 6]] </code></pre> <p>There are also <code>Arrays.equals</code> and <code>Arrays.deepEquals</code> that perform array equality comparison by their elements, among many other array-related utility methods.</p> <h3>Related questions</h3> <ul> <li><a href="https://stackoverflow.com/questions/2721033/java-arrays-equals-returns-false-for-two-dimensional-arrays">Java Arrays.equals() returns false for two dimensional arrays.</a> -- in-depth coverage</li> </ul>
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    1. COThank you for creating _the_ goto answer on the net.
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    2. CO+1 for Arrays.toString().
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