Java 11 JRE emulation

[rjeeb]

Methods to support:

String:

• lines()
• isBlank()
• format() (will not implement, this is missing deliberately from earlier versions of String)
• repeat()
• stripTrailing()
• stripLeading()
• strip()

Predicate (done):

• not()

OptionalDouble (done):

• isEmpty()

OptionalDouble (done):

• isEmpty()

OptionalLong (done):

• isEmpty()

CharSequence was split into #9991 so this could be closed as complete.

[niloc132]

Predicate and Optional* are all merged.

String.format() is likely not feasible - it requires parsing the format string at runtime, and handling the various possible patterns. That sort of code can't be optimized by the compiler without knowing ahead of time what all format strings will be.

gwt/user/super/com/google/gwt/emul/java/lang/String.java

Lines 71 to 73 in e981e97

	* <li>other methods which are not straightforward in JS
	* <ul>
	* <li>format(String format, Object... args)

https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/Formatter.html#syntax

In theory we could require that the format param will be a string literal and pre-compile the formats so that unused formatting code can be pruned. In practice, that sort of change likely wouldn't be accepted to j2cl, so we should consider carefully if we want to introduce that incompatibility.

[zbynek]

Also CharSequence.chars is already implemented:

gwt/user/super/com/google/gwt/emul/java/lang/CharSequence.java

Line 41 in 22ff07e

default IntStream chars() {

[niloc132]

Closing as fixed, all emulation mentioned here is fixed (CharSequence methods split into
#9991 for later followup).