> The string concatenation of java.base module is implemented based on
> StringBuilder, which will result in extra object allocation and slow
> performance. We can solve this problem by using String.concat method and
> StringConcatHelper to provide concat method.
>
> for example,
>
> * use "+"
>
> class ClassDesc {
> default String displayName() {
> c.displayName() + "[]".repeat(depth)
> }
> }
>
>
> bytecode:
>
> 106: new #40 // class java/lang/StringBuilder
> 109: dup
> 110: invokespecial #42 // Method
> java/lang/StringBuilder."<init>":()V
> 113: aload_2
> 114: invokeinterface #195, 1 // InterfaceMethod
> displayName:()Ljava/lang/String;
> 119: invokevirtual #50 // Method
> java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
> 122: ldc #198 // String []
> 124: iload_1
> 125: invokevirtual #200 // Method
> java/lang/String.repeat:(I)Ljava/lang/String;
> 128: invokevirtual #50 // Method
> java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
> 131: invokevirtual #53 // Method
> java/lang/StringBuilder.toString:()Ljava/lang/String;
> 134: areturn
>
>
> * use String#concat
>
> c.displayName().concat("[]".repeat(depth))
>
>
> bytecode:
>
> 112: ldc #198 // String []
> 114: iload_1
> 115: invokevirtual #200 // Method
> java/lang/String.repeat:(I)Ljava/lang/String;
> 118: invokevirtual #86 // Method
> java/lang/String.concat:(Ljava/lang/String;)Ljava/lang/String;
Shaojin Wen has updated the pull request incrementally with three additional
commits since the last revision:
- more concat
- Suggestions from @ExE-Boss
- concat Object value
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/20705/files
- new: https://git.openjdk.org/jdk/pull/20705/files/16ec24a8..ea8c814e
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=20705&range=01
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=20705&range=00-01
Stats: 25 lines in 6 files changed: 7 ins; 7 del; 11 mod
Patch: https://git.openjdk.org/jdk/pull/20705.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/20705/head:pull/20705
PR: https://git.openjdk.org/jdk/pull/20705
