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8325730: StringBuilder.toString allocation for the empty String

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Reviewed-by: jlaskey, shade
This commit is contained in:
Claes Redestad 2024-02-20 20:28:55 +00:00
parent aa792eabab
commit d2590c69b4
4 changed files with 25 additions and 5 deletions
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5
src/java.base/share/classes/java/lang/StringBuffer.java
View file

@ -1,5 +1,5 @@
/* /*
* Copyright (c) 1994, 2023, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 1994, 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -735,6 +735,9 @@ import jdk.internal.vm.annotation.IntrinsicCandidate;
@Override @Override
@IntrinsicCandidate @IntrinsicCandidate
public synchronized String toString() { public synchronized String toString() {
if (length() == 0) {
return "";
}
if (toStringCache == null) { if (toStringCache == null) {
return toStringCache = new String(this, null); return toStringCache = new String(this, null);
} }

7
src/java.base/share/classes/java/lang/StringBuilder.java
View file

@ -1,5 +1,5 @@
/* /*
* Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2003, 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -471,8 +471,11 @@ public final class StringBuilder
@Override @Override
@IntrinsicCandidate @IntrinsicCandidate
public String toString() { public String toString() {
if (length() == 0) {
return "";
}
// Create a copy, don't share the array // Create a copy, don't share the array
return new String(this); return new String(this, null);
} }
/** /**

8
test/micro/org/openjdk/bench/java/lang/StringBuffers.java
View file

@ -1,5 +1,5 @@
/* /*
* Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2014, 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -80,4 +80,10 @@ public class StringBuffers {
return blaha.substring(30, 35); return blaha.substring(30, 35);
} }
StringBuffer sb = new StringBuffer();
@Benchmark
public String emptyToString() {
return sb.toString();
}
} }

10
test/micro/org/openjdk/bench/java/lang/StringBuilders.java
View file

@ -1,5 +1,5 @@
/* /*
* Copyright (c) 2014, 2019, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2014, 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -364,6 +364,11 @@ public class StringBuilders {
return sbUtf16.charAt(charAt_index); return sbUtf16.charAt(charAt_index);
} }
@Benchmark
public String emptyToString(Data data) {
return data.sbEmpty.toString();
}
@State(Scope.Thread) @State(Scope.Thread)
public static class Data { public static class Data {
int i = 0; int i = 0;
@ -380,6 +385,7 @@ public class StringBuilders {
} }
} }
StringBuilder sbEmpty;
String str; String str;
String utf16Str; String utf16Str;
CharSequence cs; CharSequence cs;
@ -398,6 +404,8 @@ public class StringBuilders {
} }
private void generateData() { private void generateData() {
sbEmpty = new StringBuilder(length);
char[] chars = "abcdefghijklmnopqrstuvwxyz0123456789".toCharArray(); char[] chars = "abcdefghijklmnopqrstuvwxyz0123456789".toCharArray();
StringBuilder sb = new StringBuilder(length); StringBuilder sb = new StringBuilder(length);