Hello, I think we can reduce allocation rate for j.l.Character.toString() by calling String.valueOf(char) instead of String.valueOf(char[]).
Current implementation creates char[] with one char which is later decoded into byte[]. Instead String.valueOf(char) decodes char directly consuming less memory. I've used benchmark [1] and on my machine got those results (JDK 14): Benchmark Mode Score Error Units CharacterToStringBenchmark.toString_utf8 avgt 14.723 ± 1.354 ns/op CharacterToStringBenchmark.valueOf_utf8 avgt 7.678 ± 0.601 ns/op CharacterToStringBenchmark.toString_latin avgt 10.992 ± 1.371 ns/op CharacterToStringBenchmark.valueOf_latin avgt 7.844 ± 1.044 ns/op CharacterToStringBenchmark.toString_utf8:·gc.alloc.rate.norm avgt 96.003 ± 0.001 B/op CharacterToStringBenchmark.valueOf_utf8:·gc.alloc.rate.norm avgt 48.002 ± 0.001 B/op CharacterToStringBenchmark.toString_latin:·gc.alloc.rate.norm avgt 72.003 ± 0.001 B/op CharacterToStringBenchmark.valueOf_latin:·gc.alloc.rate.norm avgt 48.002 ± 0.001 B/op Patch is below. With best regards, Sergey Tsypanov [1] https://github.com/stsypanov/strings/blob/master/src/jmh/java/tsypanov/strings/character/CharacterToStringBenchmark.java diff --git a/src/java.base/share/classes/java/lang/Character.java b/src/java.base/share/classes/java/lang/Character.java --- a/src/java.base/share/classes/java/lang/Character.java +++ b/src/java.base/share/classes/java/lang/Character.java @@ -3285,7 +3285,7 @@ "SYMBOLS AND PICTOGRAPHS EXTENDED-A", "SYMBOLSANDPICTOGRAPHSEXTENDED-A"); - private static final int blockStarts[] = { + private static final int[] blockStarts = { 0x0000, // 0000..007F; Basic Latin 0x0080, // 0080..00FF; Latin-1 Supplement 0x0100, // 0100..017F; Latin Extended-A @@ -8068,7 +8068,7 @@ UNKNOWN, // E01F0..10FFFF }; - private static HashMap<String, Character.UnicodeScript> aliases; + private static final HashMap<String, Character.UnicodeScript> aliases; static { aliases = new HashMap<>((int)(153 / 0.75f + 1.0f)); aliases.put("ADLM", ADLAM); @@ -8421,8 +8421,7 @@ * @return a string representation of this object. */ public String toString() { - char buf[] = {value}; - return String.valueOf(buf); + return toString(value); } /**
