RFR: 8357289: Break down the String constructor into smaller methods [v3]

[Chen Liang]

On Sun, 25 May 2025 06:27:14 GMT, Shaojin Wen <swen at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/String.java line 703:
>> 
>>> 701:                 throw new Error(x);
>>> 702:             }
>>> 703:             if (COMPACT_STRINGS) {
>> 
>> Now we can call other constructors of String, so instead of having this manual handling of char[], we can call `return new String(ca, 0, caLen, null)`. Same for the `clen` version above.
>
> private String(char[] value, int off, int len, Void sig) {
>         if (len == 0) {
>             this.value = "".value;
>             this.coder = "".coder;
>             return;
>         }
>         if (COMPACT_STRINGS) {
>             byte[] val = StringUTF16.compress(value, off, len);
>             this.coder = StringUTF16.coderFromArrayLen(val, len);
>             this.value = val;
>             return;
>         }
>         this.coder = UTF16;
>         this.value = StringUTF16.toBytes(value, off, len);
>     }
> 
> 
> This constructor has additional processing logic for len == 0. 
> 
> ValueObject may be used here in the future. I think it is better to keep the original structure.

I thought this would both increase cleaniness and reduce code size of the decode method. @minborg What do you think? This also removes one of the switches on COMPACT_STRING.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25290#discussion_r2106193216