Before Java 5, comments were Java’s only flexible mechanism for associating metadata with application elements. But because the compiler ignores them, comments are not available at runtime.

This value includes all blanks ... length cannot be resolved or is not a field Also be sure to initialize the Java String before you invoke the length() method, or else a NullPointer runtime exception ...

Java strings are created and manipulated through the string class. Once created, a string is immutable -- its value cannot be changed. A string is sequence of characters. A class is a user-defined ...