Question

I am running a NetBeans profile of a recursive operation that includes creating a class with a java.lang.String field. In the classes list, in the profile heap dump, the number of String fields corresponds to the number of classes created as expected, however there are also a similar number of char[] instances. The char arrays account for nearly 70% of the memory usage(!) whilst the String field accounts for about 7%.

What is going on here? And how can I reduce the number of char[] instances?

Thanks

Answer 1

Take a look at the String source code. The String object itself contains a cached hash code, a count of the number of characters (again, for optimisation purposes), an offset (since a String.substr() points to the original string data) and the character array, which contains the actual string data. Hence your metrics showing that String consumes relatively little, but the majority of memory is taken by the underlying character arrays.