What determines when softly referenced objects are flushed?
Starting with Java HotSpot VM implementations in J2SE 1.3.1, softly reachable objects will remain alive for some amount of time after the last time they were referenced. The default value is one second of lifetime per free megabyte in the heap. This value can be adjusted using the -XX:SoftRefLRUPolicyMSPerMB flag, which accepts integer values representing milliseconds. For example, to change the value from one second to 2.5 seconds, use this flag: -XX:SoftRefLRUPolicyMSPerMB=2500 The Java HotSpot Server VM uses the maximum possible heap size (as set with the -Xmx option) to calculate free space remaining. The Java Hotspot Client VM uses the current heap size to calculate the free space. This means that the general tendency is for the Server VM to grow the heap rather than flush soft references, and -Xmx therefore has a significant effect on when soft references are garbage collected. On the other hand, the Client VM will have a greater tendency to flush soft references rather than grow
