Java 内存安全问题的注意事项

public class HeapOOM {
    static class ObjectInHeap{
    }
    public static void main(String[] args) {
        List<ObjectInHeap> list = new ArrayList();
        while (true) {
            list.add(new ObjectInHeap());
        }
    }
}

public class StackSOF {
    private int stackLength = 1;
    public void stackLeak() {
        stackLength++;
        stackLeak();
    }
    public static void main(String[] args) {
        StackSOF sof = new StackSOF();
        try {
            sof.stackLeak();
        } catch (Throwable e) {
            System.out.println("Stack Length: " + sof.stackLength);
            throw e;
        }
    }
}

public class StackOOM {
    private void dontStop() {
        while (true) {
        }
    }
    public void stackLeadByThread() {
        while (true) {
            Thread thread = new Thread(new Runnable() {
                @Override
                public void run() {
                    dontStop();
                }
            });
            thread.start();
        }
    }
    public static void main(String[] args) {
        StackOOM stackOOM = new StackOOM();
        stackOOM.stackLeadByThread();
    }
}

public class RuntimeConstantPoolOOM {
    public static void main(String[] args) {
        // 使用List保持着常量池的引用，避免Full GC回收常量池
        List<String> list = new ArrayList<String>();
        int i = 0;
        while (true) {
            // intern()方法使String放入常量池
            list.add(String.valueOf(i++).intern());
        }
    }
}

public class MethodAreaOOM {
    static class ObjectInMethod {
    }
    public static void main(final String[] args) {
        // 借助CGLib实现
        while (true) {
            Enhancer enhancer = new Enhancer();
            enhancer.setSuperclass(ObjectInMethod.class);
            enhancer.setUseCache(false);
            enhancer.setCallback(new MethodInterceptor() {
                @Override
                public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
                    return methodProxy.invokeSuper(o, objects);
                }
            });
            enhancer.create();
        }
    }
}

public class DirectMemoryOOM {
    private static final int _1MB = 1024 * 1024;
    public static void main(String[] args) throws IllegalAccessException {
        Field unsafeField = Unsafe.class.getDeclaredFields()[0];
        unsafeField.setAccessible(true);
        Unsafe unsafe = (Unsafe) unsafeField.get(null);
        while (true) {
            unsafe.allocateMemory(_1MB);
        }
    }
}

jmap -dump:fORMat=b,file=/xx/xx/xx.hprof pid