ThreadGroup.allowThreadSuspension dates from JDK 1.1 and the Classic VM. The method appears to have controlled whether threads were suspended when the GC failed. It appears to have interacted with a callback mechanism that could potentially free memory, allowing the GC to retry. The method was never specified and not clear how anything could have used it without being tied to the Classic VM implementation.

The method was deprecated and changed to do nothing in JDK 1.2. It was deprecated for removal in Java 14.

A corpus analysis of 30378800 classes in 130997 artifacts found 0 usages of this method.