1. A computer-implemented method for multi-byte compressed string representation, the computer-implemented method comprising: defining a package protected final static boolean control field, enableStringCompression, in a String class, which identifies whether compression is one of enabled or disabled, wherein enableStringCompression is initialized on managed runtime startup; defining a package protected static control field, stringCompressionFlag, which identifies whether a decompressed string has been created when running with compression enabled; in response to pattern matching by a compiler, noping entire tests based on a null setting of the stringCompressionFlag and registering a class loading assumption on a nop location; in response to a determination of supplied arguments to a String class constructor not being compressible, creating a decompressed string and initializing a stringCompressionFlag static field; defining compiler-recognized intrinsically reducible endian-aware helper methods for reading and writing byte and character values in an array; defining compiler-recognized intrinsically reducible helper methods associated with widening, narrowing, truncation, conversion and masking operations; enhancing String class constructors which accept collections of character values to determine whether a supplied collection of characters is compressible, and when determined to be uncompressible creating a decompressed string and initializing the stringCompressionFlag static field causing all class load assumptions to be triggered, overwriting all nopable patch points; employing a sign bit of a count integer field of a String object, representing a number of code-points the respective String object contains, as a flag bit set to one for decompressed string representations when compression is enabled, wherein masking and testing of this flag bit is noped using the stringCompressionFlag and an associated class load assumption; providing a set of predetermined alternative package protected string constructors and operations; and checking a predetermined location to determine whether supplied arguments to a String class constructor are compressible.