How to get JVM default max heap size

To get JVM default max heap size, use the following command:

$ java -XX:+PrintFlagsFinal -version | grep HeapSize
    uintx ErgoHeapSizeLimit                         = 0                                   {product}
    uintx HeapSizePerGCThread                       = 87241520                            {product}
    uintx InitialHeapSize                          := 262144000                           {product}
    uintx LargePageHeapSizeThreshold                = 134217728                           {product}
    uintx MaxHeapSize                              := 4179623936                          {product}
java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)
$

In this case, you can see it's 4GB.

Reference:
http://stackoverflow.com/questions/12797560/command-line-tool-to-find-java-heap-size-and-memory-used-linux