{"id":2952,"date":"2016-12-14T16:11:21","date_gmt":"2016-12-14T08:11:21","guid":{"rendered":"http:\/\/www.menglanglang.cn\/?p=2952"},"modified":"2016-12-14T16:11:21","modified_gmt":"2016-12-14T08:11:21","slug":"iterator%e5%9c%a8%e8%bf%ad%e4%bb%a3%e4%b8%ad%e5%88%a0%e9%99%a4%e5%85%83%e7%b4%a0%e6%8a%9b%e5%bc%82%e5%b8%b8","status":"publish","type":"post","link":"http:\/\/www.menglanglang.cn\/?p=2952","title":{"rendered":"Iterator\u5728\u8fed\u4ee3\u4e2d\u5220\u9664\u5143\u7d20\u629b\u5f02\u5e38"},"content":{"rendered":"

Iterator \u4ec5\u7528\u4e8e\u904d\u5386\u96c6\u5408\uff0c\u672c\u8eab\u5e76\u4e0d\u63d0\u4f9b\u50cf\u96c6\u5408\u7c7b\u90a3\u6837\u88c5\u5bf9\u8c61\u7684\u80fd\u529b\u3002Iterator \u662f\u4e2a\u501f\u53e3\uff0c\u5982\u679c\u9700\u8981\u521b\u5efa\u5176\u5bf9\u8c61\uff0c\u5fc5\u987b\u6709\u4e00\u4e2a\u88ab\u8fed\u4ee3\u7684\u96c6\u5408\uff0c\u6ca1\u6709\u96c6\u5408\u7684 Iterator \u6ca1\u6709\u5b58\u5728\u7684\u4ef7\u503c\u3002<\/p>\n

\u6240\u4ee5\u8bf4\uff0cIterator \u5fc5\u987b\u4f9d\u9644\u4e8e Collection \u5bf9\u8c61\uff0c\u6709\u4e00\u4e2a Iterator \u5bf9\u8c61\uff0c\u80af\u5b9a\u5c31\u6709\u4e00\u4e2a\u4e0e\u4e4b\u5173\u8054\u7684 Collection \u5bf9\u8c61\u3002\u6587\u7ae0\u300aJava\u904d\u5386HashSet\u4e3a\u4ec0\u4e48\u8f93\u51fa\u662f\u6709\u5e8f\u7684<\/a>\u300b\u4e00\u6587\u4e2d\u5f00\u59cb\u6709\u4e2a\u4f8b\u5b50\uff0c\u53ef\u4ee5\u770b\u5230\u5728\u8fed\u4ee3 HashSet \u7684\u8fc7\u7a0b\u4e2d\u5bf9\u8fed\u4ee3\u904d\u5386\u8fdb\u884c\u8d4b\u503c\uff0c\u4f46\u6700\u540e\u8f93\u51fa\u65f6\u53d1\u73b0\u96c6\u5408\u65e0\u4efb\u4f55\u6539\u53d8\u3002\u539f\u56e0\u662f\u5728\u5bf9\u96c6\u5408\u8fdb\u884c\u8fed\u4ee3\u7684\u8fc7\u7a0b\u4e2d\uff0cIterator \u5e76\u4e0d\u662f\u628a\u96c6\u5408\u4e2d\u7684\u5143\u7d20\u672c\u8eab\u4f20\u9012\u7ed9\u8fed\u4ee3\u53d8\u91cf\uff0c\u800c\u662f\u628a\u503c\u4f20\u7ed9\u8fed\u4ee3\u53d8\u91cf\u3002<\/p>\n

\u56e0\u6b64\uff0c\u5728\u8fed\u4ee3\u96c6\u5408\u7684\u8fc7\u7a0b\u4e2d\uff0c\u5982\u679c\u5bf9\u96c6\u5408\u4e2d\u7684\u5143\u7d20\u8fdb\u884c\u64cd\u4f5c\uff0c\u5219\u4f1a\u629b\u51fa\u00a0ConcurrentModificationException \u5f02\u5e38\uff0c\u6bd4\u5982\u4ee5\u4e0b\u4ee3\u7801\uff1a<\/p>\n

\n
\n
Code<\/b>\u00a0\u00a0\u00a0View<\/a>Print<\/a><\/div>\n<\/div>\n
    \n
  1. package<\/span>\u00a0com.menglanglang.java.collection;<\/li>\n
  2. <\/li>\n
  3. import<\/span>\u00a0java.util.*;<\/li>\n
  4. \/**<\/span><\/li>\n
  5. \u00a0*\u00a0Description:<\/span><\/li>\n
  6. \u00a0*\u00a0<br\/>\u7f51\u7ad9:\u00a0<a\u00a0href=\"http:\/\/www.crazyit.org\">\u75af\u72c2Java\u8054\u76df<\/a><\/span><\/li>\n
  7. \u00a0*\u00a0<br\/>Copyright\u00a0(C),\u00a02001-2016,\u00a0Yeeku.H.Lee<\/span><\/li>\n
  8. \u00a0*\u00a0<br\/>This\u00a0program\u00a0is\u00a0protected\u00a0by\u00a0copyright\u00a0laws.<\/span><\/li>\n
  9. \u00a0*\u00a0<br\/>Program\u00a0Name:<\/span><\/li>\n
  10. \u00a0*\u00a0<br\/>Date:<\/span><\/li>\n
  11. \u00a0*\u00a0@author\u00a0Yeeku.H.Lee\u00a0kongyeeku@163.com<\/span><\/li>\n
  12. \u00a0*\u00a0@version\u00a01.0<\/span><\/li>\n
  13. \u00a0*\/<\/span><\/li>\n
  14. public<\/span>\u00a0class<\/span>\u00a0IteratorErrorTest<\/li>\n
  15. {<\/li>\n
  16. \u00a0\u00a0\u00a0\u00a0public<\/span>\u00a0static<\/span>\u00a0void<\/span>\u00a0main(String[]\u00a0args)<\/li>\n
  17. \u00a0\u00a0\u00a0\u00a0{<\/li>\n
  18. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u521b\u5efa\u96c6\u5408\u3001\u6dfb\u52a0\u5143\u7d20\u7684\u4ee3\u7801\u4e0e\u524d\u4e00\u4e2a\u7a0b\u5e8f\u76f8\u540c<\/span><\/li>\n
  19. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Collection\u00a0books\u00a0=\u00a0new<\/span>\u00a0HashSet();<\/li>\n
  20. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0books.add(\"\u8f7b\u91cf\u7ea7Java\u00a0EE\u4f01\u4e1a\u5e94\u7528\u5b9e\u6218\"<\/span>);<\/li>\n
  21. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0books.add(\"\u75af\u72c2Java\u8bb2\u4e49\"<\/span>);<\/li>\n
  22. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0books.add(\"\u75af\u72c2Android\u8bb2\u4e49\"<\/span>);<\/li>\n
  23. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u83b7\u53d6books\u96c6\u5408\u5bf9\u5e94\u7684\u8fed\u4ee3\u5668<\/span><\/li>\n
  24. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Iterator\u00a0it\u00a0=\u00a0books.iterator();<\/li>\n
  25. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0while<\/span>(it.hasNext())<\/li>\n
  26. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0{<\/li>\n
  27. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0String\u00a0book\u00a0=\u00a0(String)it.next();<\/li>\n
  28. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.out.println(book);<\/li>\n
  29. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0if<\/span>\u00a0(book.equals(\"\u75af\u72c2Android\u8bb2\u4e49\"<\/span>))<\/li>\n
  30. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0{<\/li>\n
  31. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\/\/\u00a0\u4f7f\u7528Iterator\u8fed\u4ee3\u8fc7\u7a0b\u4e2d\uff0c\u4e0d\u53ef\u4fee\u6539\u96c6\u5408\u5143\u7d20,\u4e0b\u9762\u4ee3\u7801\u5f15\u53d1\u5f02\u5e38<\/span><\/li>\n
  32. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0books.remove(book);<\/li>\n
  33. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/li>\n
  34. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0}<\/li>\n
  35. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0System.out.println(books);<\/li>\n
  36. \u00a0\u00a0\u00a0\u00a0}<\/li>\n
  37. }<\/li>\n<\/ol>\n<\/div>\n

    \u8f93\u51fa\u5f02\u5e38\u4fe1\u606f\u5982\u4e0b\uff1a<\/p>\n

    \n
    \u75af\u72c2Android\u8bb2\u4e49<\/span>
    \nException in thread \"main\" java.util.ConcurrentModificationException<\/span>
    \n at java.util.HashMap$HashIterator.nextNode(HashMap.java:1429)<\/span>
    \n at java.util.HashMap$KeyIterator.next(HashMap.java:1453)<\/span>
    \n at com.menglanglang.java.collection.IteratorErrorTest.main(IteratorErrorTest.java:27)<\/span><\/div>\n<\/blockquote>\n

    Iterator \u4f7f\u7528\u7684\u662f\u5feb\u901f\u5931\u8d25\uff08fail-fast\uff09\u673a\u5236\uff0c\u8be5\u673a\u5236\u4e00\u65e6\u76d1\u6d4b\u5230\u5728\u8fed\u4ee3\u8fc7\u7a0b\u4e2d\u96c6\u5408\u4e2d\u7684\u5143\u7d20\u88ab\u4fee\u6539\uff0c\u7acb\u5373\u629b\u51fa\u00a0ConcurrentModificationException \u5f02\u5e38\u3002\u4f46\u5982\u679c\u628a\u4e0a\u9762\u7684\u4ee3\u7801\u4e2d\uff0c\u5224\u65ad\u90e8\u5206\u6539\u4e3a\u201c\u75af\u72c2Java\u8bb2\u4e49\u201d\uff0c\u5373\u5f53\u5224\u65ad\u8fed\u4ee3\u5143\u7d20\u4e3a\u201c\u75af\u72c2Java\u8bb2\u4e49\u201d\u65f6\uff0c\u4ece\u96c6\u5408\u4e2d\u5220\u9664\u201c\u75af\u72c2Java\u8bb2\u4e49\u201d\u5143\u7d20\uff0c\u5219\u53ef\u4ee5\u770b\u5230\u5982\u4e0b\u7ed3\u679c\uff1a<\/p>\n

    \u75af\u72c2Android\u8bb2\u4e49
    \n\u8f7b\u91cf\u7ea7Java EE\u4f01\u4e1a\u5e94\u7528\u5b9e\u6218
    \n\u75af\u72c2Java\u8bb2\u4e49
    \n[\u75af\u72c2Android\u8bb2\u4e49, \u8f7b\u91cf\u7ea7Java EE\u4f01\u4e1a\u5e94\u7528\u5b9e\u6218]<\/p><\/blockquote>\n

    \u53ef\u4ee5\u770b\u5230\u5220\u9664\u6210\u529f\u4e86\uff0c\u300a\u75af\u72c2Java\u8bb2\u4e49\u300b\u4e2d\u8bf4\u5230\u53ea\u6709\u5220\u9664\u96c6\u5408\u4e2d\u7279\u5b9a\u7684\u5143\u7d20\u624d\u4f1a\u51fa\u73b0\u4e0d\u62a5\u9519\u7684\u60c5\u51b5\uff0c\u662f\u7531\u96c6\u5408\u7c7b\u7684\u5b9e\u73b0\u4ee3\u7801\u51b3\u5b9a\u7684\uff0c\u4e0d\u80fd\u5c31\u8f7b\u6613\u5730\u4e0b\u96c6\u5408\u8fed\u4ee3\u8fc7\u7a0b\u4e2d\u53ef\u4ee5\u4fee\u6539\u5176\u4e2d\u7684\u5143\u7d20\u7684\u7ed3\u8bba\u3002<\/p>\n

    \u6211\u53c8\u62ff\u6587\u7ae0\u300aJava\u904d\u5386HashSet\u4e3a\u4ec0\u4e48\u8f93\u51fa\u662f\u6709\u5e8f\u7684<\/a>\u300b\u4e00\u6587\u4e2d\u540e\u9762\u7684\u4f8b\u5b50\u8bd5\u4e86\u8bd5\uff0c\u8be5\u4f8b\u5b50\u53ea\u662f\u5728\u6bcf\u4e2a\u4e32\u524d\u52a0\u4e86\u4e2a\u201c\u5b5f\u201d\u5b57\u3002<\/p>\n

    \u7ed3\u679c\u662f\u53ef\u4ee5\u5220\u9664\u201c\u5b5f\u8f7b\u91cf\u7ea7Java EE\u4f01\u4e1a\u5e94\u7528\u5b9e\u6218\u201d\u7684\u5143\u7d20\uff0c\u800c\u5220\u9664\u201c\u5b5f\u75af\u72c2Java\u8bb2\u4e49\u201d\u5219\u62a5\u9519\u3002\u8054\u7cfb\u524d\u9762\u6587\u7ae0\u4e2d\u63d0\u5230\u7684\u6709\u5e8f<\/strong>\u95ee\u9898\uff0c\u6211\u53d1\u73b0\u5f53\u5220\u9664\u8f93\u51fa\u4e2d\u7684\u6700\u540e\u4e00\u4e2a\u5143\u7d20\u65f6\uff0c\u662f\u53ef\u4ee5\u5220\u9664\u7684\uff0c\u9664\u4e86\u6700\u540e\u4e00\u4e2a\u5143\u7d20\uff0c\u5176\u5b83\u5143\u7d20\u7684\u5220\u9664\u90fd\u629b\u5f02\u5e38\u3002\u6240\u4ee5\u6000\u7740\u597d\u5947\u5fc3\uff0c\u770b\u4e86\u4e0b Java \u6e90\u7801\u4e2d\uff0cHashSet \u7c7b\u5bf9 remove() \u65b9\u6cd5\u7684\u5b9e\u73b0\uff0c\u6e90\u7801\u5982\u4e0b\uff1a<\/p>\n

    \n
    <\/div>\n
      \n
    1. public<\/span>\u00a0boolean<\/span>\u00a0remove(Object\u00a0o)\u00a0{<\/li>\n
    2. \u00a0\u00a0\u00a0\u00a0return<\/span>\u00a0map.remove(o)==PRESENT;<\/li>\n
    3. }<\/li>\n<\/ol>\n<\/div>\n

      \u800c PRESENT \u5e38\u91cf\u7684\u5b9a\u4e49\u5982\u4e0b\uff1a<\/p>\n

      private static final Object PRESENT = new Object();<\/code><\/p>\n

      \u4e3a\u4f55\u96c6\u5408 map \u5f53\u5176 remove \u8f93\u51fa\u65f6\u7684\u6700\u540e\u4e00\u4e2a\u5143\u7d20\u65f6\uff0c\u53ef\u4ee5\u8fd4\u56de true\uff0c\u800c remove \u5176\u5b83\u5143\u7d20\u65f6\uff0c\u76f4\u63a5\u629b\u51fa\u5f02\u5e38\uff1f<\/p>\n

      \u6709\u4eba\u89e3\u91ca\u9053\uff1a\u5728\u6267\u884c\u4e86 remove \u65b9\u6cd5\u4e4b\u540e\uff0c\u518d\u53bb\u6267\u884c\u5faa\u73af iter.next() \u7684\u65f6\u5019\uff0c\u62a5java.util.ConcurrentModificationException\uff0c\u5982\u679c remove \u7684\u662f\u6700\u540e\u4e00\u6761\uff0c\u5c31\u4e0d\u4f1a\u518d\u53bb\u6267\u884c next() \u64cd\u4f5c\u4e86\uff0c\u6240\u4ee5\u4e0d\u4f1a\u62a5\u9519\u3002<\/p>\n

      \u5176\u5b9e\uff0c\u770b\u5176\u00a0AbstractList.java \u6e90\u7801\uff0c\u4e3b\u8981\u6709\u5982\u4e0b\u65b9\u6cd5\uff1a<\/p>\n

      \n
      <\/div>\n
        \n
      1. private<\/span>\u00a0void<\/span>\u00a0checkForComodification()\u00a0{<\/li>\n
      2. \u00a0\u00a0\u00a0\u00a0if<\/span>\u00a0(this<\/span>.modCount\u00a0!=\u00a0l.modCount)<\/li>\n
      3. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0throw<\/span>\u00a0new<\/span>\u00a0ConcurrentModificationException();<\/li>\n
      4. }<\/li>\n<\/ol>\n<\/div>\n

        \u800c\u5728 next()\uff0cadd()\uff0cremove()\uff0csize() \u7b49\u65b9\u6cd5\u4e2d\u90fd\u4f1a\u8c03\u7528\u8be5\u9a8c\u8bc1\u65b9\u6cd5\uff0c\u5982\u679c if \u4e2d\u7684\u5224\u65ad\u6210\u7acb\uff0c\u5219\u7acb\u523b\u629b\u51fa\u5f02\u5e38\uff0c\u5177\u4f53\u8be6\u7ec6\u8bf7\u53c2\u770b\u6e90\u7801\u3002<\/p>\n

        \u4ece\u672c\u8d28\u4e0a\u89e3\u91ca\u539f\u56e0\uff1a\u00a0\u00a0<\/span><\/p>\n

        Iterator\u00a0\u662f\u5de5\u4f5c\u5728\u4e00\u4e2a\u72ec\u7acb\u7684\u7ebf\u7a0b\u4e2d\uff0c\u5e76\u4e14\u62e5\u6709\u4e00\u4e2a\u00a0mutex\u00a0\u9501\u3002\u00a0Iterator\u00a0\u88ab\u521b\u5efa\u4e4b\u540e\u4f1a\u5efa\u7acb\u4e00\u4e2a\u6307\u5411\u539f\u6765\u96c6\u5408\u7684\u5355\u94fe\u7d22\u5f15\u8868\uff0c\u5f53\u539f\u6765\u7684\u96c6\u5408\u6570\u91cf\u53d1\u751f\u53d8\u5316\u65f6\uff0c\u8fd9\u4e2a\u7d22\u5f15\u8868\u7684\u5185\u5bb9\u4e0d\u4f1a\u540c\u6b65\u6539\u53d8\uff0c\u5f53\u7d22\u5f15\u6307\u9488\u5f80\u540e\u79fb\u52a8\u7684\u65f6\u5019\u5c31\u627e\u4e0d\u5230\u8981\u8fed\u4ee3\u7684\u5bf9\u8c61\uff0c\u6309\u7167\u00a0fail-fast\u00a0\u539f\u5219\u00a0Iterator\u00a0\u4f1a\u9a6c\u4e0a\u629b\u51fa\u00a0java.util.ConcurrentModificationException\u00a0\u5f02\u5e38\u3002\u00a0\u00a0<\/strong><\/p>\n

        \u6240\u4ee5\u00a0Iterator\u00a0\u5728\u5de5\u4f5c\u7684\u65f6\u5019\u662f\u4e0d\u5141\u8bb8\u88ab\u8fed\u4ee3\u7684\u5bf9\u8c61\u88ab\u6539\u53d8\u7684\uff0c\u4f46\u53ef\u4ee5\u4f7f\u7528\u00a0Iterator\u00a0\u672c\u8eab\u7684\u65b9\u6cd5\u00a0remove()\u00a0\u6765\u5220\u9664\u5bf9\u8c61\uff0c\u00a0Iterator.remove()\u00a0\u65b9\u6cd5\u4f1a\u5728\u5220\u9664\u5f53\u524d\u8fed\u4ee3\u5bf9\u8c61\u7684\u540c\u65f6\u7ef4\u62a4\u7d22\u5f15\u7684\u4e00\u81f4\u6027\u3002\u00a0<\/strong><\/p>\n

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