Exceptions indicating an attempt to violate the boundaries of a managed-memory environment are handled by the runtime of said environment, in this case the JVM. The JVM is its own process, which is running your application's IL. Should a program attempt to make a call that extends the call stack beyond the limits, or allocate more memory than the JVM can reserve, the runtime itself will inject an exception, which will cause the call stack to be unwound. Regardless of the amount of memory your program currently needs, or how deep its call stack, the JVM will have allocated enough memory within its own process bounds to create said exception and inject it into your code.

Graham Borland似乎是对的:至少我的JVM显然重用了OutOfMemoryErrors。为了测试这一点，我写了一个简单的测试程序:

class OOMTest {
    private static void test (OutOfMemoryError o) {
        try {
            for (int n = 1; true; n += n) {
                int[] foo = new int[n];
            }
        } catch (OutOfMemoryError e) {
            if (e == o)
                System.out.println("Got the same OutOfMemoryError twice: " + e);
            else test(e);
        }
    }
    public static void main (String[] args) {
        test(null);
    }
}

运行它会产生如下输出:

$ javac OOMTest.java && java -Xmx10m OOMTest 
Got the same OutOfMemoryError twice: java.lang.OutOfMemoryError: Java heap space

顺便说一句，我正在运行的JVM (Ubuntu 10.04)是这样的:

$ java -version
java version "1.6.0_26"
Java(TM) SE Runtime Environment (build 1.6.0_26-b03)
Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02, mixed mode)

编辑:我试着看看如果我使用以下程序强制JVM完全耗尽内存会发生什么:

class OOMTest2 {
    private static void test (int n) {
        int[] foo;
        try {
            foo = new int[n];
            test(n * 2);
        }
        catch (OutOfMemoryError e) {
            test((n+1) / 2);
        }
    }
    public static void main (String[] args) {
        test(1);
    }
}

事实证明，它似乎是永远循环的。然而，奇怪的是，尝试用Ctrl+C终止程序却不起作用，而只给出以下消息:

Java HotSpot(TM) 64位服务器虚拟机警告:Java .lang. outofmemoryerror发生异常，向处理器发送SIGINT信号-虚拟机可能需要强制终止

Exceptions indicating an attempt to violate the boundaries of a managed-memory environment are handled by the runtime of said environment, in this case the JVM. The JVM is its own process, which is running your application's IL. Should a program attempt to make a call that extends the call stack beyond the limits, or allocate more memory than the JVM can reserve, the runtime itself will inject an exception, which will cause the call stack to be unwound. Regardless of the amount of memory your program currently needs, or how deep its call stack, the JVM will have allocated enough memory within its own process bounds to create said exception and inject it into your code.

摘自JVM规范第3.5.2章:

如果可以动态扩展Java虚拟机堆栈，并且尝试进行扩展，但可用的内存不足，或者可用的内存不足，无法为新线程创建初始Java虚拟机堆栈，则Java虚拟机抛出OutOfMemoryError异常。

每个Java虚拟机都必须保证抛出OutOfMemoryError错误。这意味着，即使没有堆空间，它也必须能够创建OutOfMemoryError的实例(或预先创建一个)。

虽然它不需要保证有足够的内存来捕获它并打印一个漂亮的堆栈跟踪…

除了

您添加了一些代码来表明，如果JVM必须抛出多个OutOfMemoryError，那么它可能会耗尽堆空间。但是这样的实现会违反上面的要求。

抛出的OutOfMemoryError实例不要求是唯一的或按需创建的。JVM可以在启动期间准备一个OutOfMemoryError实例，并在耗尽堆空间时抛出这个实例——在正常环境中只有一次。换句话说:我们看到的OutOfMemoryError实例可能是一个单例。

上次我使用Java并使用调试器时，堆检查器显示JVM在启动时分配了OutOfMemoryError实例。换句话说，它在程序有机会开始使用(更不用说耗尽)内存之前分配对象。

为了进一步澄清@Graham Borland的回答，从功能上讲，JVM在启动时这样做:

private static final OutOfMemoryError OOME = new OutOfMemoryError();

稍后，JVM执行以下Java字节码之一:'new'， 'anewarray'，或'multianewarray'。这条指令导致JVM在内存不足的情况下执行一些步骤:

Invoke a native function, say allocate(). allocate() attempts to allocate memory for some a new instance of a particular class or array. That allocation request fails, so the JVM invokes another native function, say doGC(), which attempts to do garbage collection. When that function returns, allocate() tries to allocate memory for the instance once again. If that fails(*), then the JVM, within allocate(), simply does a throw OOME;, referring to the OOME that it instantiated at startup. Note that it did not have to allocate that OOME, it just refers to it.

显然，这些都不是字面上的步骤;它们在实现中会因JVM的不同而不同，但这是高级的想法。

在失败之前，这里发生了大量的工作。JVM将尝试清除SoftReference对象，在使用分代收集器时尝试直接分配到年老代，以及可能的其他事情，比如终结。