Revert "Delete Matrix.java"

This reverts commit 1d7501fdae45011a4eb179a5ce0eafe0f5477dad.
Revert "Revert "Delete Matrix.java""

This reverts commit 2c42667d74956453bb49b95e1d741f0e9d19daa8.
Revert "Revert "Revert "Delete Matrix.java"""

This reverts commit 51601babf316e2f6cfbe18d6de625b6c60bb6fc2.