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Improvements to Program Execution Speed

Documentation Contents

The following are some of the changes made to improve the program execution speed and general runtime performance of the Java 2 SDK and Java 2 Runtime Environment. Links to relevant bug reports on the BugParade web site are provided were applicable for further information.

Improved Performance for readUTF and writeUTF - The implementations of the readUTF and writeUTF methods of DataInputStream and DataInputStream have been modified to improve performance. This is a fix for bug number 4219771 on the BugParade web site.

Improved Performance of JScrollPane Painting - The implementation of JScrollPane has been improved so that it does not cause excessive painting and screen flashing when double buffering is not used.

Improved JTable Performance - The performance of the JTable's column-handling functionality has been improved. Previously, the performance of the operations of adding columns or recalculating column widths did not scale well as the number of columns became large. The implementation has been changed to improve scalability. This is a fix for bug number 4223642 on the BugParade web site.

Paint Coalescing - Painting performance has been enhanced through the implementation of an improved paint coalescing algorithm. Areas that require repainting are coalesced into a single, non-rectangular repaint area as they are posted to the event queue. This has the effect batching repaints, executing multiple repaints simultaneously in a manner more efficient than in previous releases.

Frame Resizing - Resizing of top-level frames has been improved.

Internal Frame Blitting - By using Graphics.copyArea calls, Swing's DefaultDesktopManager now needs to redraw far less when frames are dragged.

Performance Enhancements in BigIntenger - Class java.math.BigInteger has been reimplemented in pure Java programming-language code. Previously, BigInteger's implementation was based on the Plumb C library. The new implementation performs all standard operations much faster than the old implementation. The speed-up realized in the new implemenation can be as much as 5x or more, depending on the operation being performed.

Provision for Better-Performing Numeric Operations - The Java 2 Platform now contains two classes which provide API for performing general numeric operations.

java.lang.StrictMath - Class java.lang.StrictMath is a renaming of class java.lang.Math from previous versions of the Java platform, but otherwise retains the previous specification of Math. In particular, it is defined to return bit-for-bit reproducible results in all implementations.
java.lang.Math - Class java.lang.Math provides the same set of API as does class StrictMath. However, unlike some of the numeric functions of class StrictMath, all implementations of the equivalent functions of class Math are not defined to return the bit-for-bit same results, but can vary within specified constraints. This relaxation permits better-performing implementations where strict reproducibility is not required.

Please send comments to: jdk-comments@eng.sun.com