byse type support for complex (planar) number arithmethics
this is a pretty old topic for the Java community, but still one that has not been addressed since the end of the 90's: support for complex numbers as base data types.
The issue is that modelling complex numbers as classes implies that complex number instances become references. While this is not an issue with most other kinds of objects, it is one for computing intense algorithms like fourier transformations, which in turn has so far inhibited Java's use in areas such as physics or audio/video processing.
As far as I understand, the major obstacle of including complex data types into the JVM so far has been guaranteing result precision for complex functions (as modelled in java.lang.Math). Another (minor) one is that the comparison operators (<, >, ...) are difficult to define properly for complex numbers.
However, I think the Java Community could already gain tremendously in the above areas by introducing only a primitive complex number datatype along with the basic numeric operators (+, -, *, /), implicit type conversion, a simple wrapper type and type boxing/unboxing. Optionally, some base functions like abs() and arg() would be nice, but as with all other complex functions they can be provided by project code rather than Java SE.
For example, such a datatype would allow a single System.arraycopy() operation to copy a complete array of complex numbers in one go, much faster than possible today. Also, algorithms dealing with complex numbers would face no more issues with tons of temporarily created object instances.
The reason I'm posting this here is that I'm unsure on whom to address with this issue. So if you have some thoughts about the general concept or the right person to approach with this ... raise your voice. :)
Former JCP Spec Lead JSR086