RFR: 8265418: Clean-up redundant null-checks of Class.getPackageName() [v3]

[Сергей Цыпанов]

On Thu, 27 May 2021 10:08:17 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> One more thing I'm thinking about (not to be done in this PR of course) is to move call to `String.intern()` from where it is now in `Class.getPackageName()`
>> 
>> public String getPackageName() {
>>     String pn = this.packageName;
>>     if (pn == null) {
>>         Class<?> c = this;
>>         while (c.isArray()) {
>>             c = c.getComponentType();
>>         }
>>         if (c.isPrimitive()) {
>>             pn = "java.lang";
>>         } else {
>>             String cn = c.getName();
>>             int dot = cn.lastIndexOf('.');
>>             pn = (dot != -1) ? cn.substring(0, dot).intern() : "";    // <---
>>         }
>>         this.packageName = pn;
>>     }
>>     return pn;
>> }
>> 
>> to `packageName` field assignement like
>> 
>> this.packageName = pn.intern();
>> 
>> this would add two more Strings (`""` and `"java.lang"`) into string table and allow to avoid `String.equals()` in favour of `==` call when comparing package names. What do you think?
>
> String literals are implicitly interned:
> 
> System.out.println("" == new String("")); // false
> System.out.println("" == new String("").intern()); // true
> System.out.println("java.lang" == new String("java.lang")); // false
> System.out.println("java.lang" == new String("java.lang").intern()); // true
> 
> 
> So we could already use `==`  instead of `equals` when evaluating the result of `getPackageName`, which might be a good optimization in some places (`ReflectionFactory::isSamePackage` shows up in profiles of some reflection-related benchmarks).

Done!

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PR: https://git.openjdk.java.net/jdk/pull/3571