Checking the JVM Heap Allocation Quickly from the Command Line

One liner for checking the JVM heap memory allocation:

java -server -XX:+UnlockDiagnosticVMOptions -XX:+PrintFlagsFinal -version | grep -i heapsize

On a 32 bit JVM:

uintx ErgoHeapSizeLimit                    = 0                {product}
uintx InitialHeapSize                     := 63763392         {product}
uintx LargePageHeapSizeThreshold           = 134217728        {product}
uintx MaxHeapSize                         := 1020214272       {product}
java version "1.6.0_22"
Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
Java HotSpot(TM) Server VM (build 17.1-b03, mixed mode)

(1 gigabyte allocated)

On a 64 bit JVM:

uintx ErgoHeapSizeLimit                    = 0                {product}
uintx InitialHeapSize                     := 128755328        {product}
uintx LargePageHeapSizeThreshold           = 134217728        {product}
uintx MaxHeapSize                         := 2060085248       {product}
java version "1.6.0_22"
Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03, mixed mode)

(2 gigabytes allocated)

A 32 bit JVM is allocated 1G and a 64 bit JVM is allocated 2G to the max heap space by default.