{"id":2339,"date":"2023-06-27T15:33:03","date_gmt":"2023-06-27T07:33:03","guid":{"rendered":"https:\/\/xinchewhd.com.cn\/?p=2339"},"modified":"2023-06-27T15:33:03","modified_gmt":"2023-06-27T07:33:03","slug":"java%e6%b3%9b%e5%9e%8b%e4%b8%ad%e7%9a%84t%e3%80%81e%e3%80%81k%e3%80%81v%e3%80%81%ef%bc%9f%e9%80%9a%e9%85%8d%e7%ac%a6%ef%bc%8c%e4%bd%a0%e7%a1%ae%e5%ae%9a%e9%83%bd%e4%ba%86%e8%a7%a3%e5%90%97%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/xinchewhd.com.cn\/index.php\/java\/java%e6%b3%9b%e5%9e%8b%e4%b8%ad%e7%9a%84t%e3%80%81e%e3%80%81k%e3%80%81v%e3%80%81%ef%bc%9f%e9%80%9a%e9%85%8d%e7%ac%a6%ef%bc%8c%e4%bd%a0%e7%a1%ae%e5%ae%9a%e9%83%bd%e4%ba%86%e8%a7%a3%e5%90%97%ef%bc%9f\/","title":{"rendered":"Java\u6cdb\u578b\u4e2d\u7684T\u3001E\u3001K\u3001V\u3001\uff1f\u901a\u914d\u7b26\uff0c\u4f60\u786e\u5b9a\u90fd\u4e86\u89e3\u5417\uff1f"},"content":{"rendered":"
\n

\u5927\u5bb6\u597d\uff0c\u6211\u662f\u4e00\u5b89~<\/span>
<\/p>\n

\u524d\u8a00<\/span><\/h2>\n
Java \u6cdb\u578b\uff08generics\uff09\u662f JDK 5 \u4e2d\u5f15\u5165\u7684\u4e00\u4e2a\u65b0\u7279\u6027, \u6cdb\u578b\u63d0\u4f9b\u4e86\u7f16\u8bd1\u65f6\u7c7b\u578b\u5b89\u5168\u68c0\u6d4b\u673a\u5236\uff0c\u8be5\u673a\u5236\u5141\u8bb8\u5f00\u53d1\u8005\u5728\u7f16\u8bd1\u65f6\u68c0\u6d4b\u5230\u975e\u6cd5\u7684\u7c7b\u578b\u3002<\/span><\/section>\n
\u6cdb\u578b\u7684\u672c\u8d28\u662f\u53c2\u6570\u5316\u7c7b\u578b\uff0c\u4e5f\u5c31\u662f\u8bf4\u6240\u64cd\u4f5c\u7684\u6570\u636e\u7c7b\u578b\u88ab\u6307\u5b9a\u4e3a\u4e00\u4e2a\u53c2\u6570\u3002<\/span><\/section>\n

\u6cdb\u578b\u5e26\u6765\u7684\u597d\u5904<\/span><\/h2>\n
\u5728\u6ca1\u6709\u6cdb\u578b\u7684\u60c5\u51b5\u7684\u4e0b\uff0c\u901a\u8fc7\u5bf9\u7c7b\u578b Object \u7684\u5f15\u7528\u6765\u5b9e\u73b0\u53c2\u6570\u7684\u201c\u4efb\u610f\u5316\u201d\uff0c\u201c\u4efb\u610f\u5316\u201d\u5e26\u6765\u7684\u7f3a\u70b9\u662f\u8981\u505a\u663e\u5f0f\u7684\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\uff0c\u800c\u8fd9\u79cd\u8f6c\u6362\u662f\u8981\u6c42\u5f00\u53d1\u8005\u5bf9\u5b9e\u9645\u53c2\u6570\u7c7b\u578b\u53ef\u4ee5\u9884\u77e5\u7684\u60c5\u51b5\u4e0b\u8fdb\u884c\u7684\u3002\u5bf9\u4e8e\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u9519\u8bef\u7684\u60c5\u51b5\uff0c\u7f16\u8bd1\u5668\u53ef\u80fd\u4e0d\u63d0\u793a\u9519\u8bef\uff0c\u5728\u8fd0\u884c\u7684\u65f6\u5019\u624d\u51fa\u73b0\u5f02\u5e38\uff0c\u8fd9\u662f\u672c\u8eab\u5c31\u662f\u4e00\u4e2a\u5b89\u5168\u9690\u60a3\u3002<\/span><\/section>\n
\u90a3\u4e48\u6cdb\u578b\u7684\u597d\u5904\u5c31\u662f\u5728\u7f16\u8bd1\u7684\u65f6\u5019\u80fd\u591f\u68c0\u67e5\u7c7b\u578b\u5b89\u5168\uff0c\u5e76\u4e14\u6240\u6709\u7684\u5f3a\u5236\u8f6c\u6362\u90fd\u662f\u81ea\u52a8\u548c\u9690\u5f0f\u7684\u3002<\/span><\/section>\n
public<\/span> class<\/span> GlmapperGeneric<\/span><<\/span>T><\/span><\/span> {<\/span>
\t\tprivate<\/span> T t;<\/span>
    public<\/span> void<\/span> set<\/span>(<\/span>T t)<\/span> {<\/span> this<\/span>.<\/span>t =<\/span> t;<\/span> }<\/span>
    public<\/span> T get<\/span>()<\/span> {<\/span> return<\/span> t;<\/span> }<\/span>
  
    public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String[]<\/span> args)<\/span> {<\/span>
        \/\/ do nothing<\/span>
    }<\/span>

  \/**
    * \u4e0d\u6307\u5b9a\u7c7b\u578b
    *\/<\/span>
  public<\/span> void<\/span> noSpecifyType<\/span>(){<\/span>
    GlmapperGeneric glmapperGeneric =<\/span> new<\/span> GlmapperGeneric<\/span>();<\/span>
    glmapperGeneric.<\/span>set<\/span>(<\/span>\"test\"<\/span>);<\/span>
    \/\/ \u9700\u8981\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362<\/span>
    String test =<\/span> (<\/span>String)<\/span> glmapperGeneric.<\/span>get<\/span>();<\/span>
    System.<\/span>out.<\/span>println<\/span>(<\/span>test);<\/span>
  }<\/span>

  \/**
    * \u6307\u5b9a\u7c7b\u578b
    *\/<\/span>
  public<\/span> void<\/span> specifyType<\/span>(){<\/span>
    GlmapperGeneric<<\/span>String><\/span><\/span> glmapperGeneric =<\/span> new<\/span> GlmapperGeneric<\/span>();<\/span>
    glmapperGeneric.<\/span>set<\/span>(<\/span>\"test\"<\/span>);<\/span>
    \/\/ \u4e0d\u9700\u8981\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362<\/span>
    String test =<\/span> glmapperGeneric.<\/span>get<\/span>();<\/span>
    System.<\/span>out.<\/span>println<\/span>(<\/span>test);<\/span>
  }<\/span>
}<\/span><\/span><\/code><\/pre>\n
\u4e0a\u9762\u8fd9\u6bb5\u4ee3\u7801\u4e2d\u7684 specifyType \u65b9\u6cd5\u4e2d \u7701\u53bb\u4e86\u5f3a\u5236\u8f6c\u6362\uff0c\u53ef\u4ee5\u5728\u7f16\u8bd1\u65f6\u5019\u68c0\u67e5\u7c7b\u578b\u5b89\u5168\uff0c\u53ef\u4ee5\u7528\u5728\u7c7b\uff0c\u65b9\u6cd5\uff0c\u63a5\u53e3\u4e0a\u3002<\/span><\/section>\n
\u6cdb\u578b\u4e2d\u901a\u914d\u7b26<\/span><\/h2>\n
\u6211\u4eec\u5728\u5b9a\u4e49\u6cdb\u578b\u7c7b\uff0c\u6cdb\u578b\u65b9\u6cd5\uff0c\u6cdb\u578b\u63a5\u53e3\u7684\u65f6\u5019\u7ecf\u5e38\u4f1a\u78b0\u89c1\u5f88\u591a\u4e0d\u540c\u7684\u901a\u914d\u7b26\uff0c\u6bd4\u5982 T\uff0cE\uff0cK\uff0cV \u7b49\u7b49\uff0c\u8fd9\u4e9b\u901a\u914d\u7b26\u53c8\u90fd\u662f\u4ec0\u4e48\u610f\u601d\u5462\uff1f<\/span><\/section>\n
\u5e38\u7528\u7684 T\uff0cE\uff0cK\uff0cV\uff0c\uff1f<\/span><\/strong><\/span><\/section>\n
\u672c\u8d28\u4e0a\u8fd9\u4e9b\u4e2a\u90fd\u662f\u901a\u914d\u7b26\uff0c\u6ca1\u5565\u533a\u522b\uff0c\u53ea\u4e0d\u8fc7\u662f\u7f16\u7801\u65f6\u7684\u4e00\u79cd\u7ea6\u5b9a\u4fd7\u6210\u7684\u4e1c\u897f\u3002\u6bd4\u5982\u4e0a\u8ff0\u4ee3\u7801\u4e2d\u7684 T \uff0c\u6211\u4eec\u53ef\u4ee5\u6362\u6210 A-Z \u4e4b\u95f4\u7684\u4efb\u4f55\u4e00\u4e2a \u5b57\u6bcd\u90fd\u53ef\u4ee5\uff0c\u5e76\u4e0d\u4f1a\u5f71\u54cd\u7a0b\u5e8f\u7684\u6b63\u5e38\u8fd0\u884c\uff0c\u4f46\u662f\u5982\u679c\u6362\u6210\u5176\u4ed6\u7684\u5b57\u6bcd\u4ee3\u66ff T \uff0c\u5728\u53ef\u8bfb\u6027\u4e0a\u53ef\u80fd\u4f1a\u5f31\u4e00\u4e9b\u3002\u901a\u5e38\u60c5\u51b5\u4e0b\uff0cT\uff0cE\uff0cK\uff0cV\uff0c\uff1f\u662f\u8fd9\u6837\u7ea6\u5b9a\u7684\uff1a<\/span><\/section>\n
\n
\uff1f\u8868\u793a\u4e0d\u786e\u5b9a\u7684 java \u7c7b\u578b
T (type) \u8868\u793a\u5177\u4f53\u7684\u4e00\u4e2ajava\u7c7b\u578b
K V (key value) \u5206\u522b\u4ee3\u8868java\u952e\u503c\u4e2d\u7684Key Value
E (element) \u4ee3\u8868Elemen<\/p>\n<\/blockquote>\n
<\/span><\/section>\n
\uff1f\u65e0\u754c\u901a\u914d\u7b26<\/span><\/strong><\/span><\/section>\n
\u5148\u4ece\u4e00\u4e2a\u5c0f\u4f8b\u5b50\u770b\u8d77\uff0c<\/span>\u6211\u6709\u4e00\u4e2a\u7236\u7c7bAnimal\u548c\u51e0\u4e2a\u5b50\u7c7b\uff0c\u5982\u72d7\u3001\u732b\u7b49\uff0c\u73b0\u5728\u6211\u9700\u8981\u4e00\u4e2a\u52a8\u7269\u7684\u5217\u8868\uff0c\u6211\u7684\u7b2c\u4e00\u4e2a\u60f3\u6cd5\u662f\u50cf\u8fd9\u6837\u7684\uff1a<\/span><\/section>\n
List<<\/span>Animal><\/span><\/span> listAnimals<\/span><\/code><\/pre>\n
\u4f46\u662f\u8001\u677f\u7684\u60f3\u6cd5\u786e\u5b9e\u8fd9\u6837\u7684\uff1a<\/span><\/section>\n
List<?<\/span> extends<\/span> Animal<\/span>><\/span> listAnimals<\/span><\/code><\/pre>\n
\u4e3a\u4ec0\u4e48\u8981\u4f7f\u7528\u901a\u914d\u7b26\u800c\u4e0d\u662f\u7b80\u5355\u7684\u6cdb\u578b\u5462\uff1f\u901a\u914d\u7b26\u5176\u5b9e\u5728\u58f0\u660e\u5c40\u90e8\u53d8\u91cf\u65f6\u662f\u6ca1\u6709\u4ec0\u4e48\u610f\u4e49\u7684\uff0c\u4f46\u662f\u5f53\u4f60\u4e3a\u4e00\u4e2a\u65b9\u6cd5\u58f0\u660e\u4e00\u4e2a\u53c2\u6570\u65f6\uff0c\u5b83\u662f\u975e\u5e38\u91cd\u8981\u7684\u3002<\/span><\/section>\n
static<\/span> int<\/span> countLegs (<\/span>List<?<\/span> extends<\/span> Animal<\/span> ><\/span> animals )<\/span> {<\/span>
    int<\/span> retVal =<\/span> 0<\/span>;<\/span>
    for<\/span> (<\/span> Animal animal :<\/span> animals )<\/span>
    {<\/span>
        retVal +=<\/span> animal.<\/span>countLegs<\/span>();<\/span>
    }<\/span>
    return<\/span> retVal;<\/span>
}<\/span>

static<\/span> int<\/span> countLegs1 (<\/span>List<<\/span> Animal ><\/span> animals ){<\/span>
    int<\/span> retVal =<\/span> 0<\/span>;<\/span>
    for<\/span> (<\/span> Animal animal :<\/span> animals )<\/span>
    {<\/span>
        retVal +=<\/span> animal.<\/span>countLegs<\/span>();<\/span>
    }<\/span>
    return<\/span> retVal;<\/span>
}<\/span>

public<\/span> static<\/span> void<\/span> main<\/span>(<\/span>String[]<\/span> args)<\/span> {<\/span>
    List<<\/span>Dog><\/span><\/span> dogs =<\/span> new<\/span> ArrayList<\/span><><\/span>();<\/span>
 \t\/\/ \u4e0d\u4f1a\u62a5\u9519<\/span>
    countLegs<\/span>(<\/span> dogs );<\/span>
\t\/\/ \u62a5\u9519<\/span>
    countLegs1<\/span>(<\/span>dogs);<\/span>
}<\/span><\/span><\/code><\/pre>\n
\u5f53\u8c03\u7528 countLegs1 \u65f6\uff0c\u5c31\u4f1a\u98d8\u7ea2\uff0c\u63d0\u793a\u7684\u9519\u8bef\u4fe1\u606f\u5982\u4e0b\uff1a<\/span><\/section>\n