String: optimize String.format() performance

[superajun-wsj]

No description provided.

[Copilot]

Pull request overview

This pull request introduces a comprehensive implementation of formatting infrastructure to optimize String.format() performance. The changes add core Java formatting capabilities including a full Formatter class implementation, the Integer class with parsing/formatting methods, and a new String.repeat() method.

Changes:

• Adds complete Formatter class (~5400 lines) for printf-style formatting
• Implements Integer class with string conversion and parsing utilities
• Introduces String.repeat() method for efficient string repetition
• Adds new exception classes: IllegalFormatArgumentIndexException and NumberFormatException

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
IllegalFormatArgumentIndexException.java	New exception for invalid format argument indices
Formatter.java	Complete formatter implementation with extensive documentation
String.java	Added repeat() method for string repetition
NumberFormatException.java	Exception class with factory methods for parsing errors
Integer.java	Integer wrapper class with conversion and parsing methods

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Missing period at the end of the parameter description. The Javadoc should read "The value of a corresponding illegal argument index." to maintain consistency with Java documentation standards.

[Copilot]

Typo in Javadoc comment. "Deterime" should be spelled "Determine".

Suggested change

	// Deterime the number of bits to keep.
	// Determine the number of bits to keep.