Which one is indicating the exact memory use for java application

Which one is indicating the exact memory use for java application

I have a java application. The issue now I take a heap using the jmap and
I also got this codes running in my application.Both are giving me
different values. The runtime is showing out of 256mb which is what I have
assigned as initial and maximum memory? I want to detect is there any
memory leakage but the runtime is fluctuating and whereas the one from
heap is keep increasing in small amount? Any help on this?
long memory = runtime.totalMemory() - runtime.freeMemory();
System.out.println("\n\nUsed memory is bytes: " +
memory);
//Print the jvm heap size.
long heapSize = runtime.totalMemory();
System.out.println("\n\nHeap Size = " + heapSize);
int mb = 1024*1024;
System.out.println("##### Heap utilization
statistics [MB] #####");
//Print used memory
System.out.println("Used Memory:"
+ (runtime.totalMemory() -
runtime.freeMemory()) / mb);
//Print free memory
System.out.println("Free Memory:"
+ runtime.freeMemory() / mb);
//Print total available memory
System.out.println("Total Memory:" +
runtime.totalMemory() / mb);
//Print Maximum available memory
System.out.println("Max Memory:" +
runtime.maxMemory() / mb);