【2017年整理】Java垃圾回收.ppt

JVM Garbage Collection;JVM introduction Java Runtime Areas Garbage Collection Examples QA;What’s JVM? The abstract specification A concrete implementation Sun HotSpot Bea JRockit IBM J9 A runtime instance. JVM JRE JDK JVM: Translates Java byte codes and executes them as native code on the client machine. JRE: includes JVM and runtime libraries JDK: Includes JRE and development tools: like javac etc.;Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.;Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.;Memory for the class type information, like Constant pool, Field information ,Method information , class (static) variables etc All threads share the same method area Also called Permanent Generation in HotSpot Possible Error: java.lang.OutOfMemoryError: PermGen full ;JVM store a constant pool for each type including literals (string, integer, and floating point constants) and symbolic references Example ;Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.;Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.;Memory for the new class instance One heap for one JVM instance, all threads share it Main area for GC Possible Error: java.lang.OutOfMemoryError: Java heap space ;When a new thread is launched, the Java Virtual Machine creates a new Java stack for the thread All the data on the Java stack is private to that thread, can’t be accessed by other thread;stack frame: local variables primitive types and a reference type Size would be 1 word or 2 words(long, double) Word will be 4 byte in 32-bit machine, 8 byte in 64-bit operand stack frame data data to support constant pool resolution normal method return, exception dispatch;Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyri