JVM系列（二）各区域的OOM

　　stack的内存溢出demo，无限递归：

public class StackOOM {

    private static void fun(){
        fun();
    }
    
    /**
     * VM arg  -Xss128K
     * @param args
     */
    public static void main(String[] args) {
        fun();
    }

}

 　　direct memory：

public class DirectMemoryOOM {

    static int ONE_MB = 1024*1024;
    
    /**
     * -XX:MaxDirectMemorySize=5M
     * @param args
     * @throws InterruptedException
     */
    public static void main(String[] args) throws InterruptedException {
        List<ByteBuffer> list = new ArrayList<ByteBuffer>();
        
        for(int i=0; i<ONE_MB;++i){
            ByteBuffer buffer = ByteBuffer.allocateDirect(ONE_MB*128);        
            list.add(buffer);
            System.out.println("分派第"+(i+1)+" 个128MB");
        }
                    
    }

}

　　heap：

public class HeapOOM {

    static int MB = 1024*1024;
    
    /**
     * -Xmx16M
     * @param args
     */
    public static void main(String[] args) {
        
        List<Object> list = new ArrayList<Object>();
        
        for(int i=0; i<1000; ++i){
            ByteBuffer bb = java.nio.ByteBuffer.allocate(MB);
            list.add(bb);
            System.out.println("分派第"+(i+1)+" MB");
        }

    }
}

　　常量池：

public class ConstantPoolOOM {

    /**
     * -XX:MaxPermSize=10M
     * @param args
     */
    public static void main(String[] args) {
        List<Object> list = new ArrayList<Object>();
        
        for(int i=0; i<1000; ++i){
            list.add(UUID.randomUUID().toString().intern());
            System.out.println("分派第"+(i+1)+" 个");
        }
    }

}

　　方法区（借助cglib，大量的字节码加强，从而撑爆方法区）：

public class MethodAreaOOM {

    static class OOMObject {

    }

    /**
     * -XX:MaxPermSize=10M
     * @param args
     */
    public static void main(String[] args) {

        for (int i = 0; i < 9999; ++i) {
            Enhancer enhancer = new Enhancer();
            enhancer.setSuperclass(OOMObject.class);
            enhancer.setUseCache(false);
            enhancer.setCallback(new MethodInterceptor() {
                public Object intercept(Object obj, Method method,
                        Object[] args, MethodProxy proxy) throws Throwable {
                    return proxy.invokeSuper(obj, args);
                }
            });
            enhancer.create();
        }
    }
}

　　具体代码见github：https://github.com/emmerichLuang/differentOOM