{"id":1791,"date":"2018-07-18T18:23:04","date_gmt":"2018-07-18T10:23:04","guid":{"rendered":"http:\/\/ufqi.com\/blog\/?p=1791"},"modified":"2018-07-19T13:45:57","modified_gmt":"2018-07-19T05:45:57","slug":"java-foreach-final","status":"publish","type":"post","link":"https:\/\/ufqi.com\/blog\/java-foreach-final\/","title":{"rendered":"-Java forEach\u4e2d Lambda Expr\u4e2d\u7684 final\u53d8\u91cf\u8981\u6c42"},"content":{"rendered":"

\u672c\u6587\u662f\u5173\u4e8e -Java Lambda Expression\u5728forEach\u65b9\u6cd5\u7684\u5e94\u7528\u8ba8\u8bba\u3002\u5bf9\u6bd4\u5176\u4ed6\u7f16\u7a0b\u8bed\u8a00\u7684foreach \u64cd\u4f5c(\u6587\u672b\u9644\u5e267\u79cd\u4e3b\u8981\u7f16\u7a0b\u8bed\u8a00\u7684Loop HashMap by forEach\u7684\u7a0b\u5e8f\u7247\u6bb5)\uff0cJava 8\u5f15\u5165\u7684\u8fd0\u7528 Lambda Expression\u65b9\u5f0f\u7684 forEach\u64cd\u4f5c\u65b9\u6cd5\u662f\u6700\u63a5\u8fd1\u8bed\u8a00\u6240\u8981\u8868\u8fbe\u7684\u672c\u610f\uff0c\u4e14\u7b80\u6d01\u3001\u76f4\u63a5\u3002
\u5728\u6301\u7eed\u4f18\u5316 -GWA2 in -Java<\/a> \u8fc7\u7a0b\u4e2d\uff0c\u7531\u4e8e -GWA2 \u591a\u5c42\u7ed3\u6784\u8bbe\u8ba1\uff0c\u5c42\u95f4\u6570\u636e\u4f20\u9012\u5f88\u591a\u4f9d\u8d56Map\/HashMap\u5b8c\u6210\uff0c\u7ecf\u5e38\u7528\u5230\u8fd9\u4e2a forEach \u5e76\u78b0\u5230\u4e00\u4e9b\u95ee\u9898(\u5f15\u5165\u5916\u90e8\u53d8\u91cf\uff0c\u6709\u6761\u4ef6\u7b5b\u9009\u53ca\u7ec8\u6b62\u7b49)\uff0c\u5179\u8bb0\u5f55\u76f8\u5173\u63a2\u7d22\u8fc7\u7a0b\u5982\u4e0b\u3002<\/p>\n

\u901a\u5e38\u5728 -Java \u4e2d\u904d\u5386\u4e00\u4e2a\u6570\u636e\u96c6\u5408\u662f\u5e38\u89c1\u7684\u64cd\u4f5c\u573a\u666f\uff0c\u6bd4\u5982\u904d\u5386\u6570\u7ec4 (-R\/G2ST<\/a>\u00a0<\/b>)\uff1a<\/p>\n

\n
int[] numbers = \r\n             {1,2,3,4,5,6,7,8,9,10};\r\nfor (int item : numbers) {\r\n    System.out.println(\"Count is: \" + item);\r\n}<\/pre>\n<\/blockquote>\n
\u518d\u6bd4\u5982\u5e38\u89c4\u7684\u501f\u52a9 keySet\u904d\u5386\u4e00\u4e2akey-value\u7ed3\u6784\u7684 Map \/ Hash, \u54c8\u5e0c (-R\/k2SP<\/a>\u00a0<\/b>)\uff1a<\/p>\n
\n
for (KeyType key : m.keySet()){\r\n    System.out.println(key+\", \"+m.get(key));
}<\/pre>\n<\/blockquote>\n
-R\/k2SP \u5217\u4e3e\u4e86\u4e09\u79cd\u65b9\u6cd5\u8fdb\u884c\u904d\u5386key-value \u7684Map, \u5b9e\u9645\u4e0a\u6839\u636e\u00a0-R\/92SS<\/a>\u00a0 <\/b>\u9875\u9762\u4e0a\u7b2c\u4e8c\u4e2a\u56de\u7b54\u6240\u8fdb\u884c\u7684\u6d4b\u8bd5\uff0c\u5927\u6982\u6709\u5341\u591a\u79cd\u65b9\u6cd5\u53ef\u4ee5\u5b9e\u73b0\u904d\u5386\u4e00\u4e2a key-value \u7684Map. \u8fd9\u4e48\u591a\u65b9\u6cd5\u4e2d\uff0c\u53c8\u4ee5 forEach \u7684\u8868\u8fbe\u6700\u4e3a\u76f4\u63a5\u3001\u9ad8\u6548\uff0c\u6240\u4ee5\u63a8\u8350\u4f7f\u7528 Map.forEach .<\/p>\n
forEach \u672c\u8d28\u4e0a\u662f\u5efa\u9020\u4e00\u4e2a Lambda Expression \u5e76\u8fdb\u884c\u8fd0\u7b97\uff0c\u5176\u4e2d Map.forEach \u7b49\u540c\u7684\u8868\u8fbe\u5f0f\u4e5f\u662f\u9488\u5bf9\u00a0 keySet\u7684\u8c03\u7528(\u00a0-R\/V2SQ<\/a>\u00a0)\u3002<\/p>\n
\n
\/\/- Map.forEach is equivalent to:
for (Map.Entry<K, V> entry : map.entrySet())\r\n     action.accept(entry.getKey(), entry.getValue());<\/code><\/pre>\n
\/\/- an example
HashMap<String, Integer> hm = new HashMap<String, Integer>();
hm.forEach((key, val)->{
\u00a0 \u00a0 System.out.println(key+”, “+val);
\u00a0 \u00a0 });<\/p>\n<\/blockquote>\n
\u7531\u4e8e Lambda Expression \u662f\u4e00\u4e2a enclosing scope\uff0c\u5b83\u4e0e\u4ee3\u7801\u533a\u5757\u5916\u7684\u6c9f\u901a\u6210\u4e3a\u95ee\u9898\uff0c\u5916\u90e8\u53d8\u91cf\u65e0\u6cd5\u5728 Lambda \u5185\u90e8\u8c03\u7528\uff0c\u5185\u90e8\u53d8\u91cf\u4e5f\u65e0\u6cd5\u5728\u5916\u90e8\u8bbf\u95ee\u5230\u3002\u5728\u8fd9\u8fd1\u4e4e\u9694\u79bb\u7684\u8fd0\u884c\u65f6\u73af\u5883\u91cc\uff0c\u8fd8\u7559\u4e86final\u53d8\u91cf\u53ef\u4ee5\u7a7f\u884c\u7684\u7f1d\u9699\uff0c\u5982\u679c\u8981\u5b9e\u73b0\u5c06Lambda Expr\u4e0e\u5916\u90e8\u53d8\u91cf\u8fdb\u884c\u6570\u636e\u4ea4\u6362\uff0c\u5c31\u9700\u8981\u5728\u4ee3\u7801\u533a\u5757\u5916\u90e8\u5b9a\u4e49final\u7c7b\u578b\u53d8\u91cf\u4f5c\u4e3a\u6570\u636e\u4fe1\u606f\u8f7d\u4f53\u3002\u5e38\u89c1\u7684\u5e94\u7528\u6709\u5982\u4e0b\u4e24\u4e2a\u573a\u666f.<\/p>\n
    \n
  1. \u5c06Map\/HashMap\u7684\u6570\u636e\u904d\u5386\u5e76\u52a0\u5de5
    <\/strong>\u4f8b\u5b50\u7a0b\u5e8f\uff1a
    \n
    HashMap<String, Integer> hm = new HashMap<String, Integer>();
    final HashMap<String, Integer> hm2 = new HashMap<String, Integer>();
    hm.forEach((key, val)->{
    \u00a0 \u00a0 System.out.println(key+”, “+val);
    \u00a0 \u00a0 hm2.put(key, val + 1);
    \u00a0 \u00a0 });<\/p><\/blockquote>\n
    \u501f\u52a9 Lambda Expression \u5bf9 final\u53d8\u91cf\u7684\u652f\u6301\uff0c\u53ef\u4ee5\u5bb9\u6613\u5730\u5c06\u904d\u5386\u5e76\u52a0\u5de5\u540e\u7684\u6570\u636e\u4e2d\u8f6c\u53d6\u51fa\u505a\u8fdb\u4e00\u6b65\u7684\u64cd\u4f5c. 
    final \u53d8\u91cf\u7531\u4e8e\u65e0\u6cd5\u518d\u6b21\u51fa\u73b0\u5728\u8d4b\u503c\u8bed\u53e5\u7684\u5de6\u8fb9\uff0c\u4e5f\u5373\u65e0\u6cd5\u5bf9\u5bf9\u8c61\u505a\u518d\u6b21\u8d4b\u503c\u64cd\u4f5c\u3002\u4f46\u8fd9\u4e0d\u5f71\u54cd\u6211\u4eec\u540e\u7eed\u5c06 hm2\u7684\u503c\u8fdb\u884c\u904d\u5386\u6216\u8005\u5c06\u5176\u590d\u5236\u5230\u53e6\u5916\u4e00\u4e2a\u975efinal\u7684\u5bf9\u8c61\u4e2d\u53bb\uff0c\u5982\u4e0a\u4f8b\u4e2d\u7684 hm.
    \u540c\u6837\u5730\uff0c\u4f5c\u4e3afinal\u7684 hm2 \u65e0\u6cd5\u6574\u4f53\u88ab\u8d4b\u503c\uff0c\u4f46\u53ef\u4ee5\u5bf9\u5176\u672c\u8eab\u8fdb\u884c\u64cd\u4f5c\uff0c\u5982\u4e0a\u4f8b\u4e2d\u7684\uff0c\u901a\u8fc7 hm2.put \u5c06\u67d0\u4e2a\u5143\u7d20\u653e\u5165\u8fd9\u4e2a\u5bb9\u5668\u4e2d\u3002\u7c7b\u4f3c\u7684\u8fd8\u6709\uff0c\u6bd4\u5982 StringBuffer \u7684\u64cd\u4f5c\u3002<\/p>\n
    StringBuffer pageIdsb = new StringBuffer(“0”);
     pageList.forEach((k, v)->{
    \u00a0 \u00a0 HashMap tmphm = (HashMap)v;
    \u00a0 \u00a0 pageIdsb.append(“,”).append(tmphm.get(“id”));
    \u00a0 \u00a0 });<\/p><\/blockquote>\n
    public final class StringBuffer<\/span>\r\nextends Object<\/a>\r\nimplements Serializable<\/a>, CharSequence<\/a><\/pre>\n
    \u7531 StringBuffer \u7c7b\u7684\u5b9a\u4e49\uff08-R\/V2SQ<\/a>\u00a0<\/b>\uff09\uff0c\u6211\u4eec\u77e5\u9053\u5176\u662f final \u7c7b\uff0c\u4e8e\u662f\u5728\u521d\u59cb\u5316\u540e\uff0c\u53ef\u4ee5\u5728 Lambda Expr\u4e2d\u901a\u8fc7 pageIdsb.append \u7684\u65b9\u5f0f\u8fdb\u884c\u5176\u503c\u7684\u64cd\u4f5c\u4e0e\u53d8\u5316\u3002<\/p>\n
    <\/li>\n
  2. \u6709\u6761\u4ef6\u8fc7\u6ee4\u6216\u63a8\u51fa\u3001\u7ec8\u6b62\u904d\u5386<\/strong>
    \u5728\u904d\u5386Map\/HashMap\u7b49\u5bf9\u8c61\u96c6\u5408\u65f6\uff0c\u6709\u65f6\u5019\u9700\u8981\u6709\u6761\u4ef6\u7684\u8fc7\u6ee4\u6216\u8005\u7ec8\u6b62\uff0c\u5982\u679c\u5c06\u5916\u90e8\u7ea6\u675f\u6761\u4ef6\u5e26\u5165\uff1f 
    \u53c8\u5982\u4f55\u5b9a\u4e49\u5185\u90e8\u81ea\u5faa\u73af\u53d8\u91cf\uff1f
    \u4e00\u79cd\u53ef\u884c\u7684\u65b9\u5f0f\uff0c\u4f9d\u7136\u662f\u4f7f\u7528 final\u53d8\u91cf\uff0c\u7136\u540e\u57fa\u672c\u53d8\u91cf\u7c7b\u578b\uff0c\u5982\u679c\u5b9a\u4e49\u4e3afinal\u4e4b\u540e\u5219\u4e0d\u80fd\u88ab\u76f4\u63a5\u4fee\u6539\uff0c\u65e0\u6cd5\u6ee1\u8db3\u5faa\u73af\u4f53\u5185\u8ba1\u6570\u7684\u9700\u6c42.
    \u4e8e\u662f\u5c31\u9700\u8981\u8bbe\u8ba1\u4e00\u4e2a\u590d\u5408final\u7c7b\u7684\u53d8\u91cf\uff0c\u5176\u6210\u5458\u4e00\u4e2a\u8d1f\u8d23\u7ea6\u675f\u6761\u4ef6\uff0c\u53e6\u5916\u4e00\u4e2a\u8d1f\u8d23\u5faa\u73af\u8ba1\u6570\u3002
    \n
    HashMap<String, Integer> hm = new HashMap<String, Integer>();
    final HashMap<String, Integer> hm2 = new HashMap<String, Integer>(){{
    \u00a0 \u00a0 put(“iCount”, 0);
    \u00a0 \u00a0 put(“maxCount”, 4);
    \u00a0 \u00a0 }};
    hm.forEach((key, val)->{
    \u00a0 \u00a0 int iCount = Wht.parseInt(hm2.get(“iCount”));
    \u00a0 \u00a0 int maxCount = Wht.parseInt(hm2.get(“maxCount”));
    \u00a0 \u00a0 if(iCount < maxCount){
    \u00a0 \u00a0 \u00a0 \u00a0 System.out.println(key+”, “+val);
    \u00a0 \u00a0 }
    \u00a0 \u00a0 hm2.put(“iCount”, iCount + 1);
    \u00a0 \u00a0 });<\/p><\/blockquote>\n
    \u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u7a0b\u5e8f\u4e2d\uff0c\u6211\u4eec\u5b9a\u4e49\u4e86\u5faa\u73af\u4f53\u5185\u8ba1\u6570\u53d8\u91cf iCount \u548c \u6ee1\u8db3\u9000\u51fa\u6761\u4ef6 maxCount \u6bcf\u6b21\u5faa\u73af\u65f6\u53d6\u51fa\u5e76\u505a\u5bf9\u6bd4\uff0c\u6bcf\u6b21\u5faa\u73af\u65f6\uff0c iCount++ \u3002
    \u4e0a\u9762\u4f8b\u5b50\u7a0b\u5e8f\u4e2d\u7684 Wht.parseInt \u662f -GWA2 \u7684\u57fa\u7840\u8bbe\u65bd\u7c7b\uff0c\u53ef\u4ee5\u5728 -GWA2@Github \uff08    -R\/h2SO<\/a>\u00a0<\/b>\uff09\u4e0b\u8f7d\u5230.
    \u4e0a\u9762\u4f8b\u5b50\u7a0b\u5e8f\u4e2d\u7684hm2 \u7684\u58f0\u660e\u5b9e\u4f8b\u4e2d\uff0c\u901a\u8fc7\u6784\u9020\u65b9\u6cd5\u5e76\u4ee5\u4e00\u4e2a\u533f\u540d\u7c7b\u5b8c\u6210\u4e86\u4e24\u4e2a put\u64cd\u4f5c\u3002\u5173\u4e8e\u533f\u540d\u7c7b Anonymous Class\uff0c\u53c2\u8003 -Java \u6587\u6863\uff08    -R\/i2SP<\/a>\u00a0<\/b>\uff09\uff0c \u5728 -GWA2 in -Java \u91cc\u4e5f\u6709\u4e0d\u5c11\u5e94\u7528\u3002
    \u00a0<\/li>\n<\/ol>\n
    -Java \u4e2d\u5f15\u5165\u7684 forEach \u64cd\u4f5c\uff0c\u5c3d\u7ba1\u662f\u4ee5 Lambda Expression\u4e3a\u8f7d\u4f53\u7684\u4e00\u4e2a Consumer \/ BiConsumer\u5bf9\u8c61\uff0c\u8fd0\u884c\u5728\u4e00\u4e2a enclosing scope\uff0c\u4f9d\u9760\u53ef\u4ee5\u5916\u90e8 final \u53d8\u91cf\u8fd9\u4e2a\u6e20\u9053\uff0c\u53ef\u4ee5\u63d0\u4f9b\u5ab2\u7f8e\u5176\u4ed6\u7f16\u7a0b\u8bed\u8a00\u4e00\u6837\u7684 foreach \u6548\u679c\uff0c\u5bf9\u589e\u52a0\u7a0b\u5e8f\u53ef\u8bfb\u6027\u3001\u53ef\u7ef4\u62a4\u6027\u6709\u4e00\u5b9a\u7684\u5e2e\u52a9\uff0c\u5df2\u6709\u7684\u8bc4\u6d4b forEach\u4e5f\u8868\u73b0\u51fa\u4e0d\u9519\u7684\u6027\u80fd\uff0c\u503c\u5f97\u66f4\u591a\u5730\u5e94\u7528\u3002<\/p>\n
     <\/p>\n
    <\/p>\n
    -GWA2 \u662f\u201d\u901a\u7528\u7f51\u7edc\u5e94\u7528\u67b6\u6784( General Web Application Architeture )\u201d\uff0c\u57fa\u4e8e -GWA2 \u53ef\u4ee5\u8f7b\u4fbf\u6784\u5efa\u5404\u79cd\u7f51\u7edc\u5e94\u7528\u7a0b\u5e8f,
    \u5305\u62ec\u590d\u6742\u7684\u5728\u7ebf\u8d2d\u7269\u5546\u57ce\u3001\u00a0\u65c5\u6e38\u4ea4\u6613\u5e73\u53f0\u3001\u793e\u7fa4\u6216\u8005\u793e\u4ea4\u7f51\u7ad9\u548c\u65b0\u95fb\u8d44\u8baf\u7f51\u7ad9\u7b49\uff0c
    \u4e5f\u5305\u62ec\u5404\u79cd\u4f01\u4e8b\u4e1a\u5355\u4f4d\u7f51\u4e0a\u95e8\u6237\uff0c\u5728\u7ebf\u4ea4\u4e92\u53ca\u670d\u52a1\u4f5c\u4e1a\u7cfb\u7edf\u7b49.
    \u8fd8\u53ef\u4ee5\u5305\u62ec\u4e3aNativeApp\u505a\u670d\u52a1\u5668\u7aef\u652f\u6301, \u751a\u81f3\u662fWebApp\u7684\u5168\u90e8.
    -GWA2 \u662f\u4e3a\u6570\u4e0d\u591a\u7684\u652f\u6301\u8de8\u5f00\u53d1\u8bed\u8a00\u7684\u5e94\u7528\u6846\u67b6\uff0c\u76ee\u524d\u652f\u6301 -Java, -PHP, -Perl, -Aspx and -Python .<\/p>\n
    -GWA2 is a \u201cGeneral Web Application Architecture\u201d and based on -GWA2 developers can easily build a variety of network applications,
    including complex online shopping malls, travel trading platforms, community or social networking sites and news information sites, etc.
    Also the applications include various online portals of enterprises and institutions, online interaction and service operations systems.
    Moreover it contains server-side support for NativeApp, or even all of the WebApp.
    -GWA2 is one of the web frameworks which provide cross-language support for -Java, -PHP, -Perl, -Aspx and -Python at present.<\/p>\n
    -GWA2 is E.A.S.Y\u00a0<\/strong>
    Easy Along, Swift Yield
    <\/b>\u8f7b\u677e\u542f\u52a8, \u5feb\u901f\u4ea7\u51fa.<\/p>\n
    \n
    (1) Loop HashMap in PHP ****<\/p>\n
    \n
    $hm = array(“a”=>1, “b”=>2, “c”=>3);
    foreach($hm as $key=>$val){
    \u00a0 \u00a0 print “key:$key , val:$val\\n”;
    }<\/p>\n<\/blockquote>\n
    (2) Loop HashMap in Perl ***<\/p>\n
    \n
    my %hm = (“a”=>1, “b”=>2, “c”=>3);
    foreach my $key (keys %hm){
    \u00a0 \u00a0 my $val = $hm{$key};
    \u00a0 \u00a0 print “key:$key , val:$val\\n”;
    }<\/p>\n<\/blockquote>\n
    (3) Loop HashMap in Swift *****<\/p>\n
    \n
    let hm = [“a”:1, “b”:2, “c”:3];
    for (key, val) in hm {
    \u00a0 \u00a0 print(“key:\\(key) , val:\\(val)\\n”);
    }<\/p>\n<\/blockquote>\n
    (4) Loop HashMap in Python ***<\/p>\n
    \n
    hm = {“a”:1, “b”:2, “c”:3};
    for key in hm:
    \u00a0 \u00a0 print(“key:{} , val:{}”.format(key, hm[key]));<\/p>\n<\/blockquote>\n
    (5) Loop HashMap in C++ *<\/p>\n
    \n
    std::map<std::string, std::int> hm {
    \u00a0 \u00a0 {“a”, 1},
    \u00a0 \u00a0 {“b”, 1},
    \u00a0 \u00a0 {“c”, 3}
     };
    for(const auto& key : hm){
    \u00a0 \u00a0 std::cout << “key:” << key.first
    \u00a0 \u00a0 \u00a0 \u00a0 << ” , val:” << key.second
    \u00a0 \u00a0 \u00a0 \u00a0 << “\\n”;
     }<\/p>\n<\/blockquote>\n
    (6) Loop HashMap in JavaScript ***<\/p>\n
    \n
    var hm = {“a”:1, “b”:2, “c”:3};
    for (var key in hm){
    \u00a0 \u00a0 console.log(“key:”+key+” , val:”+hm[key]);
     };<\/p>\n<\/blockquote>\n
    (7) Loop HashMap in Java ***<\/p>\n
    \n
    HashMap<String, Integer> hm = new HashMap<String, Integer>(){{
    \u00a0 \u00a0 put(“a”, 1″);
    \u00a0 \u00a0 put(“b”, 2);
    \u00a0 \u00a0 put(“c”, 3);
    }};
    hm.forEach((key, val)->{
    \u00a0 \u00a0 System.out.println(key+”, “+val);
    \u00a0 \u00a0 });<\/p>\n<\/blockquote>\n
     <\/p>\n","protected":false},"excerpt":{"rendered":"
    \u672c\u6587\u662f\u5173\u4e8e -Java Lambda Expression\u5728forEach\u65b9\u6cd5\u7684 … \u7ee7\u7eed\u9605\u8bfb →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[42,6,2],"tags":[266,265,86,267,146,268],"_links":{"self":[{"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/posts\/1791"}],"collection":[{"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/comments?post=1791"}],"version-history":[{"count":17,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/posts\/1791\/revisions"}],"predecessor-version":[{"id":1810,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/posts\/1791\/revisions\/1810"}],"wp:attachment":[{"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/media?parent=1791"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/categories?post=1791"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ufqi.com\/blog\/wp-json\/wp\/v2\/tags?post=1791"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}