Performance Comparison between String compareTo and String equals

String.equals is used to compare strings for equality, whereas compareTo is used for a lexicographic comparison (knowing which is greater, for the purpose of sorting).
However, I was wondering under what situations compareTo might be faster than equals for the purpose of an equality check. Following are some observations. The first high figure would be due to the Hotspot native compilation.

JVM: Sun 1.4.2 (Java HotSpot(TM) Client VM (build 1.4.2-b28, mixed mode)
Source code of test html Source code of test

Test	s	t	EQUALS	COMPARETO	Analysis
1) equal substrings of a string	ABCD	ABCD	43 ms 15 ms 15 ms	7 ms 6 ms 6 ms	most likely due to extra typecast. equals's length check is also redundant here
2) content different, length same	ABCDEFG	DEFGHIJ	8 ms 7 ms 7 ms	4 ms 4 ms 4 ms	probably due to typecast and ref check in equals
3) content overlaps, length diff	ABCDEFG	ABCDEFGH	5 ms 4 ms 4 ms	9 ms 9 ms 11 ms	equals has a length check, compareTo doesnt
4) content same	ABCDEFG	ABCDEFG	23 ms 22 ms 23 ms	9 ms 8 ms 9 ms	most likely because equals does extra typecast and ref check and length check
5) content diff, length diff	ABCDEFG	abcedfgh	5 ms 4 ms 4 ms	4 ms 5 ms 8 ms	equals has a length check
6) content diff at first byte, length same	ABCDEFG	aBCEDFG	8 ms 9 ms 7 ms	4 ms 5 ms 4 ms	equals has a countdown loop thus slower
7) same reference	ABCDEFG	ABCDEFG	4 ms 4 ms 5 ms	11 ms 10 ms 11 ms	equals does a refernece check first

Notes from source code of jdk 1.4.2.:

equals():

reference comparison
typecast
length comparison
countdown loop from offset comparing char array elements

compareTo():

no length check, no reference check etc
calculates min of both lengths
if offset is the same, does a forward loop comparing char array elements
else does a countdown loop comparing char array elements

Other possible test:

try with different JVMs
try with larger strings
try different vm settings

Please give feedback, analysis, other tests to me at rahul_kumar@yahoo.com. Thanks.

Rahul Kumar, 2003-11-12