{"id":115,"date":"2015-03-31T17:46:08","date_gmt":"2015-03-31T09:46:08","guid":{"rendered":"https:\/\/ai.zhousir.top\/?p=115"},"modified":"2026-08-18T12:09:26","modified_gmt":"2026-08-18T04:09:26","slug":"java%e6%b3%9b%e5%9e%8b%e9%80%9a%e9%85%8d%e7%ac%a6%e5%92%8c%e7%b1%bb%e5%9e%8b%e5%8f%82%e6%95%b0%e7%9a%84%e8%8c%83%e5%9b%b4","status":"publish","type":"post","link":"https:\/\/ai.zhousir.top\/?p=115","title":{"rendered":"java\u6cdb\u578b\u901a\u914d\u7b26\u548c\u7c7b\u578b\u53c2\u6570\u7684\u8303\u56f4"},"content":{"rendered":"
\n

\u6cdb\u578b\u91cc\u5982\u679c\u4e0d\u9650\u5236\u7c7b\u578b\u53c2\u6570\uff0c\u5b83\u53ef\u4ee5\u63a5\u53d7\u4efb\u610f\u5df2\u5b9a\u4e49\u7684\u7c7b\u578b\u3002\u5f88\u591a\u65f6\u5019\u6211\u4eec\u53ea\u9700\u8981\u5176\u4e2d\u4e00\u90e8\u5206\uff0c\u7528\u6237\u4f20\u5165\u5176\u4ed6\u7c7b\u578b\u4f1a\u5728\u8fd0\u884c\u671f\u51fa\u9519\u3002\u672c\u8282\u5148\u9650\u5236\u7c7b\u578b\u53c2\u6570\u7684\u8303\u56f4\uff0c\u518d\u8bb2\u901a\u914d\u7b26 ?<\/code>\u3002<\/p>\n

\u4f8b\u5982\u7f16\u5199\u4e00\u4e2a\u6cdb\u578b\u65b9\u6cd5\uff0c\u8fd4\u56de Integer\u3001Double \u7b49\u6570\u7ec4\u4e2d\u7684\u6700\u5927\u503c\uff1a\u5143\u7d20\u5f97\u80fd\u53d6\u6570\u503c\uff0c\u5c31\u4e0d\u80fd\u8ba9 T \u662f\u4efb\u610f\u7c7b\u578b\u3002<\/p>\n

<\/p>\n\n\n\n\n\n\n\n\n
\u5199\u6cd5<\/th>\n\u7528\u5728\u54ea<\/th>\n\u542b\u4e49<\/th>\n<\/tr>\n<\/thead>\n
<T extends Number><\/td>\n\u58f0\u660e\u6cdb\u578b\u7c7b \/ \u65b9\u6cd5\u7684\u7c7b\u578b\u53c2\u6570<\/td>\nT \u53ea\u80fd\u662f Number \u6216\u5176\u5b50\u7c7b<\/td>\n<\/tr>\n
Point<?, ?><\/td>\n\u4f7f\u7528\u5df2\u7ecf\u58f0\u660e\u597d\u7684\u6cdb\u578b\u7c7b\u578b<\/td>\n\u5b9e\u53c2\u7c7b\u578b\u4efb\u610f\uff0c\u907f\u514d\u64e6\u6210 Object<\/td>\n<\/tr>\n
? extends Number<\/td>\n\u901a\u914d\u7b26\u4e0a\u754c<\/td>\nNumber \u53ca\u5176\u5b50\u7c7b\uff1b\u9002\u5408\u53d6\u51fa<\/td>\n<\/tr>\n
? super Number<\/td>\n\u901a\u914d\u7b26\u4e0b\u754c<\/td>\nNumber \u53ca\u5176\u7236\u7c7b\uff1b\u9002\u5408\u653e\u5165<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\u4e00\u3001\u9650\u5236\u7c7b\u578b\u53c2\u6570\u7684\u8303\u56f4<\/h2>\n

\u4e0b\u9762\u8fd9\u6bb5\u4f1a\u7f16\u8bd1\u5931\u8d25\uff1adoubleValue()<\/code> \u662f Number \u53ca\u5176\u5b50\u7c7b\u7684\u65b9\u6cd5\uff0c\u4e0d\u662f\u6240\u6709 T \u90fd\u6709\u3002<\/p>\n

public <T> T getMax(T array[]) {\n    T max = null;\n    for (T element : array) {\n        max = element.doubleValue() > max.doubleValue() ? element : max;\n    }\n    return max;\n}<\/code><\/pre>\n
\u7528 extends<\/code> \u9650\u5236\u4e0a\u9650\uff0c\u8ba9 T \u53ea\u63a5\u53d7 Number \u53ca\u5176\u5b50\u7c7b\uff08Integer\u3001Double\u3001Long \u7b49\uff1bCharacter \u4e0d\u662f Number \u7684\u5b50\u7c7b<\/strong>\uff09\u3002\u8fd9\u91cc\u7684 extends \u4e0d\u518d\u53ea\u8868\u793a\u7ee7\u627f\uff1aT \u662f\u67d0\u7c7b\u7684\u5b50\u7c7b\u578b\uff0c\u6216 T \u5b9e\u73b0\u4e86\u67d0\u63a5\u53e3\u3002\u4e0a\u754c\u82e5\u662f\u7c7b\u53ea\u80fd\u5199\u4e00\u4e2a\uff1b\u63a5\u53e3\u53ef\u4ee5\u6709\u591a\u4e2a\uff0c\u7528 &<\/code> \u5206\u9694\uff0c\u4f8b\u5982 T extends Number & Comparable<T><\/code>\u3002<\/p>\n
public <T extends Number> T getMax(T array[]) {\n    if (array == null || array.length == 0) {\n        return null;\n    }\n    T max = array[0];\n    for (int i = 1; i < array.length; i++) {\n        T element = array[i];\n        max = element.doubleValue() > max.doubleValue() ? element : max;\n    }\n    return max;\n}<\/code><\/pre>\n
max \u4e0d\u80fd\u4ece null \u8d77\u6b65\u518d\u8c03 doubleValue()<\/code>\uff0c\u5426\u5219\u7a7a\u6570\u7ec4\u6216\u7b2c\u4e00\u8f6e\u6bd4\u8f83\u4f1a\u7a7a\u6307\u9488\uff1b\u5e94\u4ece\u7b2c\u4e00\u4e2a\u5143\u7d20\u5f00\u59cb\u6bd4\u3002<\/p>\n
\u4e8c\u3001\u901a\u914d\u7b26 ?<\/h2>\n
\u4e0a\u4e00\u8282\u7528\u6cdb\u578b\u7c7b\u8868\u793a\u5750\u6807\uff0c\u5750\u6807\u53ef\u4ee5\u662f\u6574\u6570\u3001\u5c0f\u6570\u6216\u5b57\u7b26\u4e32\uff1a<\/p>\n
class Point<T1, T2> {\n    T1 x;\n    T2 y;\n    public T1 getX() { return x; }\n    public void setX(T1 x) { this.x = x; }\n    public T2 getY() { return y; }\n    public void setY(T2 y) { this.y = y; }\n}<\/code><\/pre>\n
\u82e5\u5728\u7c7b\u5916\u5b9a\u4e49 printPoint(Point p)<\/code>\uff0c\u6ca1\u6709\u5199\u51fa\u7c7b\u578b\u5b9e\u53c2\u65f6\u4f1a\u53d1\u751f\u7c7b\u578b\u64e6\u9664\uff0c\u76f8\u5f53\u4e8e Point<Object, Object><\/code>\uff0c\u548c\u4e0d\u7528\u6cdb\u578b\u5dee\u4e0d\u591a\u3002\u8981\u7528\u901a\u914d\u7b26\u8868\u793a\u201c\u4efb\u610f\u7c7b\u578b\u7684 Point\u201d\uff1a<\/p>\n
public class Demo {\n    public static void main(String[] args) {\n        Point<Integer, Integer> p1 = new Point<Integer, Integer>();\n        p1.setX(10);\n        p1.setY(20);\n        printPoint(p1);\n\n        Point<String, String> p2 = new Point<String, String>();\n        p2.setX(\"\u4e1c\u4eac180\u5ea6\");\n        p2.setY(\"\u5317\u7eac210\u5ea6\");\n        printPoint(p2);\n    }\n    public static void printPoint(Point<?, ?> p) {\n        System.out.println(\"This point is: \" + p.getX() + \", \" + p.getY());\n    }\n}<\/code><\/pre>\n
\u8fd0\u884c\u7ed3\u679c\uff1aThis point is: 10, 20\uff1bThis point is: \u4e1c\u4eac180\u5ea6, \u5317\u7eac210\u5ea6\u3002<\/p>\n
\u4e09\u3001\u901a\u914d\u7b26\u7684\u4e0a\u754c\u548c\u4e0b\u754c<\/h2>\n
\u6570\u5b57\u5750\u6807\u548c\u5b57\u7b26\u4e32\u5750\u6807\u542b\u4e49\u4e0d\u540c\uff1a\u6570\u5b57\u8868\u793a x\/y \u8f74\uff0c\u5b57\u7b26\u4e32\u8868\u793a\u7ecf\u7eac\u5ea6\u3002\u53ef\u4ee5\u518d\u9650\u5236\u901a\u914d\u7b26\u8303\u56f4\uff0c\u8ba9\u4e00\u4e2a\u65b9\u6cd5\u53ea\u63a5\u53d7\u6570\u5b57\u5750\u6807\uff0c\u53e6\u4e00\u4e2a\u53ea\u63a5\u53d7\u5b57\u7b26\u4e32\u5750\u6807\u3002<\/p>\n
public static void printNumPoint(Point<? extends Number, ? extends Number> p) {\n    System.out.println(\"x: \" + p.getX() + \", y: \" + p.getY());\n}\npublic static void printStrPoint(Point<? extends String, ? extends String> p) {\n    System.out.println(\"GPS: \" + p.getX() + \"\uff0c\" + p.getY());\n}<\/code><\/pre>\n
\u8fd0\u884c\u7ed3\u679c\uff1ax: 10, y: 20\uff1bGPS: \u4e1c\u4eac180\u5ea6\uff0c\u5317\u7eac210\u5ea6\u3002? extends Number<\/code> \u8868\u793a\u53ea\u80fd\u662f Number \u53ca\u5176\u5b50\u7c7b\u3002String \u662f final \u7c7b\uff0c\u6ca1\u6709\u5b50\u7c7b\uff0c\u56e0\u6b64 ? extends String<\/code> \u5b9e\u9645\u4e0a\u53ea\u80fd\u662f String \u672c\u8eab\u3002<\/p>\n
\u901a\u914d\u7b26\u4e0d\u4f46\u80fd\u9650\u5236\u4e0a\u9650\uff0c\u4e5f\u80fd\u9650\u5236\u4e0b\u9650\uff1a? super Number<\/code> \u8868\u793a Number \u53ca\u5176\u7236\u7c7b\u3002\u4e00\u822c\u9879\u76ee\u91cc\u5f88\u5c11\u81ea\u5df1\u8bbe\u8ba1\u6cdb\u578b\uff0c\u8fd9\u91cc\u4e3b\u8981\u662f\u5b66\u4f1a\u600e\u4e48\u8bfb\u3001\u600e\u4e48\u7528\uff0c\u7ed9\u540e\u9762\u7684\u96c6\u5408\u6559\u7a0b\u94fa\u8def\u3002<\/p>\n
\n
\u4e00\u53e5\u8bdd\u603b\u7ed3\uff1a\u58f0\u660e\u65f6\u7528 T extends \u5361\u4f4f\u7c7b\u578b\u53c2\u6570\uff1b\u4f7f\u7528\u65f6\u7528 ?\u3001? extends\u3001? super \u63cf\u8ff0\u201c\u672a\u77e5\u4f46\u6709\u8303\u56f4\u201d\u7684\u5b9e\u53c2\uff0c\u907f\u514d\u64e6\u6210\u88f8 Object\u3002<\/strong><\/p>\n<\/blockquote>\n<\/section>\n","protected":false},"excerpt":{"rendered":"
\u6cdb\u578b\u91cc\u5982\u679c\u4e0d\u9650\u5236\u7c7b\u578b\u53c2\u6570\uff0c\u5b83\u53ef\u4ee5\u63a5\u53d7\u4efb\u610f\u5df2\u5b9a\u4e49\u7684\u7c7b\u578b\u3002\u5f88\u591a\u65f6\u5019\u6211\u4eec\u53ea\u9700\u8981\u5176\u4e2d\u4e00\u90e8\u5206\uff0c\u7528\u6237\u4f20\u5165\u5176\u4ed6\u7c7b\u578b\u4f1a\u5728\u8fd0\u884c\u671f […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[17],"tags":[43,37],"_links":{"self":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/115"}],"collection":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=115"}],"version-history":[{"count":3,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/115\/revisions"}],"predecessor-version":[{"id":1357,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=\/wp\/v2\/posts\/115\/revisions\/1357"}],"wp:attachment":[{"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=115"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=115"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ai.zhousir.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=115"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}