查看现阶段JRE默认堆大小（default Heap size）

# 使用-server

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

uintx ErgoHeapSizeLimit = 0 {product}
uintx InitialHeapSize := 519327936 {product}
uintx LargePageHeapSizeThreshold = 134217728 {product}
uintx MaxHeapSize := 8311013376 {product}
java version "1.6.0_27-ea"
Java(TM) SE Runtime Environment (build 1.6.0_27-ea-b01)
Java HotSpot(TM) 64-Bit Server VM (build 20.2-b01, mixed mode)

# 使用-client
java -client -XX:+UnlockDiagnosticVMOptions -XX:+PrintFlagsFinal -version | grep -i heapsize

uintx ErgoHeapSizeLimit = 0 {product}
uintx InitialHeapSize := 519327936 {product}
uintx LargePageHeapSizeThreshold = 134217728 {product}
uintx MaxHeapSize := 8311013376 {product}
java version "1.6.0_27-ea"
Java(TM) SE Runtime Environment (build 1.6.0_27-ea-b01)
Java HotSpot(TM) 64-Bit Server VM (build 20.2-b01, mixed mode)