为什么 NPE 使用 DatatypeConverter 的静态方法?

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问题描述

我已经盯着这个短代码太久了，我一辈子都看不到它是如何在第 6 行抛出 NullPointerException 的.为什么是 NPE?

I have stared at this short code too long, and cannot for the life of me see how it can throw a NullPointerException on line 6. Why the NPE?

class ConvertTest {

    public static void main(String[] args) throws Exception {
        byte[] b = "Ha".getBytes("UTF-8");
        System.out.println("bytes: " + b.length);
        javax.xml.bind.DatatypeConverter.printBase64Binary(b);  // NPE!
    }
}

输出

bytes: 2
Exception in thread "main" java.lang.NullPointerException
        at javax.xml.bind.DatatypeConverter.printBase64Binary(DatatypeConverter.java:547)
        at ConvertTest.main(ConvertTest.java:6)
Press any key to continue . . .

更新

虽然许多错误报告都指向 1.7 变体，但我惊讶地发现 Eclipse 被配置为使用 1.6.0_32 &TextPad 找到了 1.6.0-b105 的版本(甚至没有意识到已安装！).

Update

While many of the bug reports are pointing to a 1.7 variant, I was astonished to see that Eclipse is configured to use 1.6.0_32 & TextPad has found a version of 1.6.0-b105 (didn't even realize that was installed!).

两个 JRE 都因该 NPE 失败.

Both JREs fail with that NPE.

NPE