查看JVM使用的默认的垃圾收集器

一、方法一
打印虚拟机所有参数

 1 [jms_appus@zb_10-0-55-107_lin ~]$  java -XX:+PrintFlagsFinal -version | grep :
 2      intx CICompilerCount                          := 2                                   {product}
 3     uintx InitialHeapSize                          := 62914560                            {product}
 4     uintx MaxHeapSize                              := 1006632960                          {product}
 5     uintx MaxNewSize                               := 335544320                           {product}
 6     uintx MinHeapDeltaBytes                        := 524288                              {product}
 7     uintx NewSize                                  := 20971520                            {product}
 8     uintx OldSize                                  := 41943040                            {product}
 9      bool PrintFlagsFinal                          := true                                {product}
10      bool UseCompressedClassPointers               := true                                {lp64_product}
11      bool UseCompressedOops                        := true                                {lp64_product}
12      bool UseParallelGC                            := true                                {product}
13 java version "1.8.0_45"
14 Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
15 Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

二、方法二

1 [jms_appus@zb_10-0-55-107_lin ~]$ java -XX:+PrintCommandLineFlags -version
2 -XX:InitialHeapSize=62793728 -XX:MaxHeapSize=1004699648 -XX:+PrintCommandLineFlags -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC
3 java version "1.8.0_45"
4 Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
5 Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

参数解读：

针对上述的-XX：UseParallelGC，这边我们引用《深入理解Java虚拟机：JVM高级特性与最佳实践》的介绍：

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