{"id":112,"date":"2015-03-31T17:33:02","date_gmt":"2015-03-31T09:33:02","guid":{"rendered":"https:\/\/ai.zhousir.top\/?p=112"},"modified":"2026-08-18T12:09:26","modified_gmt":"2026-08-18T04:09:26","slug":"112","status":"publish","type":"post","link":"https:\/\/ai.zhousir.top\/?p=112","title":{"rendered":"Java\u6cdb\u578b\u8be6\u89e3"},"content":{"rendered":"
\n

\u6240\u8c13\u6cdb\u578b<\/strong>\uff0c\u5c31\u662f\u201c\u5bbd\u6cdb\u7684\u6570\u636e\u7c7b\u578b\u201d\uff1a\u4e0d\u4f46\u503c\u53ef\u4ee5\u901a\u8fc7\u53c2\u6570\u4f20\u9012\uff0c\u7c7b\u578b\u4e5f\u53ef\u4ee5\u3002\u5b83\u89e3\u51b3\u7684\u662f\uff1a\u65e2\u4e0d\u60f3\u4e3a\u6bcf\u79cd\u7c7b\u578b\u5199\u4e00\u904d\u91cd\u8f7d\uff0c\u53c8\u4e0d\u613f\u4f9d\u8d56\u4e0d\u5b89\u5168\u7684\u5411\u4e0b\u8f6c\u578b\u3002<\/p>\n

Java 1.5 \u8d77\u5f15\u5165\u6cdb\u578b\uff0c\u53c2\u7167 C++ \u6a21\u677f\uff0c\u672c\u8d28\u662f\u53c2\u6570\u5316\u7c7b\u578b<\/strong>\uff08Parameterized Type\uff09\u3002\u7c7b\u578b\u53c2\u6570\u53ea\u80fd\u8868\u793a\u5f15\u7528\u7c7b\u578b\uff1b\u4f20\u5165 int\u3001double \u4e4b\u6240\u4ee5\u80fd\u8fc7\uff0c\u662f\u56e0\u4e3a\u4f1a\u81ea\u52a8\u88c5\u7bb1\u6210\u5305\u88c5\u7c7b\u3002<\/p>\n

\u4e00\u3001\u88c5\u7bb1\u3001\u62c6\u7bb1\u4e0e\u5bf9\u8c61\u7c7b\u578b\u8f6c\u6362<\/h2>\n

\u5b9a\u4e49\u53d8\u91cf\u5fc5\u987b\u5148\u58f0\u660e\u7c7b\u578b\u3002\u5047\u5982\u5750\u6807\u7684 x\u3001y \u53ef\u80fd\u662f\u6574\u6570\u3001\u5c0f\u6570\u6216\u5b57\u7b26\u4e32\uff1a<\/p>\n

x = 10\u3001y = 10\n\nx = 12.88\u3001y = 129.65\n\nx = \"\u4e1c\u7ecf180\u5ea6\"\u3001y = \"\u5317\u7eac210\u5ea6\"<\/code><\/pre>\n
\u9664\u4e86\u65b9\u6cd5\u91cd\u8f7d\uff0c\u8fd8\u53ef\u4ee5\u8d70\u81ea\u52a8\u88c5\u7bb1\u518d\u5411\u4e0a\u8f6c\u578b\uff1aint<\/code> \u88c5\u7bb1\u6210 Integer<\/code>\uff0c\u518d\u5347\u6210 Object<\/code>\u3002\u4efb\u4f55\u7c7b\u7684\u5b9e\u4f8b\u90fd\u80fd\u5347\u6210 Object\uff1a<\/p>\n
int --> Integer -->Object\n\n    int a = 10;\n\n    Integer a1 = a; \/\/\u81ea\u52a8\u88c5\u7bb1     class  Teacher extends Person{}\n\n    Object a2 = a1; \/\/\u5411\u4e0a\u8f6c\u578b      Teacher t = new Teacher();\n\n                                                Person p = t; \/\/\u5411\u4e0a\u8f6c\u578b\n\ndouble -->Double -->Object\n\nString -->Object<\/code><\/pre>\n
\u4e8e\u662f\u4e00\u4e2a\u65b9\u6cd5\u5c31\u80fd\u63a5\u6240\u6709\u7c7b\u578b\u3002\u7528 Object \u5b58\u5750\u6807\uff1a<\/p>\n
class Point{\n\n    Object x = 0;\n\n    Object y = 0;\n\n    public Object getX() {\n\n        return x;\n\n   }\n\n    public void setX(Object x) {\n\n        this.x = x;\n\n   }\n\n    public Object getY() {\n\n        return y;\n\n   }\n\n    public void setY(Object y) {\n\n        this.y = y;\n\n   }\n\n}\n\n\n\npublic class Demo {\n\n    public static void main(String[] args){\n\n        Point p = new Point();\n\n        p.setX(10);  \/\/ int -> Integer ->Object\n\n        p.setY(20);\n\n        int x = (Integer)p.getX();  \/\/ \u5fc5\u987b\u5411\u4e0b\u8f6c\u578b\n\n        int y = (Integer)p.getY();\n\n        System.out.println(\"This point is\uff1a\" + x + \", \" + y);\n\n\n\n        p.setX(25.4);  \/\/ double -> Integer ->Object\n\n        p.setY(\"\u4e1c\u4eac180\u5ea6\");\n\n        double m = (Double)p.getX();  \/\/ \u5fc5\u987b\u5411\u4e0b\u8f6c\u578b\n\n        double n = (Double)p.getY();  \/\/ \u8fd0\u884c\u671f\u95f4\u629b\u51fa\u5f02\u5e38\n\n       System.out.println(\"This point is\uff1a\" + m + \", \" + n);\n\n   }\n\n}<\/code><\/pre>\n
\u5199\u5165\u65f6\u6ca1\u95ee\u9898\uff0c\u53d6\u51fa\u5fc5\u987b\u5411\u4e0b\u8f6c\u578b\u3002\u5411\u4e0b\u8f6c\u578b\u6709\u98ce\u9669\uff0c\u7f16\u8bd1\u671f\u770b\u4e0d\u51fa\u6765\uff0c\u8fd0\u884c\u671f\u624d\u629b ClassCastException<\/code>\u3002\u4e0a\u9762\u7b2c\u4e8c\u7ec4 getY()<\/code> \u5b9e\u9645\u662f\u5b57\u7b26\u4e32\uff0c\u5374\u5f3a\u8f6c\u6210 Double\uff0c\u8fd0\u884c\u5c31\u4f1a\u70b8\u3002<\/p>\n
\u66f4\u597d\u7684\u529e\u6cd5\u662f\u6cdb\u578b\u7c7b<\/strong>\uff1a\u4efb\u610f\u7c7b\u578b\u90fd\u80fd\u63a5\uff0c\u53c8\u628a\u8f6c\u578b\u98ce\u9669\u538b\u5230\u6700\u4f4e\u3002<\/p>\n
\u4e8c\u3001\u6cdb\u578b\u7c7b<\/h2>\n
\/\/ \u5b9a\u4e49\u6cdb\u578b\u7c7b\n\nclass Point<T1, T2>{\n\n    T1 x;\n\n    T2 y;\n\n    public T1 getX() {\n\n        return x;\n\n   }\n\n    public void setX(T1 x) {\n\n        this.x = x;\n\n   }\n\n    public T2 getY() {\n\n        return y;\n\n   }\n\n    public void setY(T2 y) {\n\n        this.y = y;\n\n   }\n\n}\n\n\n\npublic class Demo {\n\n    public static void main(String[] args){\n\n        \/\/ \u5b9e\u4f8b\u5316\u6cdb\u578b\u7c7b\n\n       Point<Integer, Integer> p1 = new Point<Integer, Integer>();\n\n       p1.setX(10);\n\n       p1.setY(20);\n\n        int x = p1.getX();\n\n        int y = p1.getY();\n\n       System.out.println(\"This point is\uff1a\" + x + \", \" + y);\n\n\n\n       Point<Double, String> p2 = new Point<Double, String>();\n\n       p2.setX(25.4);\n\n       p2.setY(\"\u4e1c\u4eac180\u5ea6\");\n\n        double m = p2.getX();\n\n        String n = p2.getY();\n\n       System.out.println(\"This point is\uff1a\" + m + \", \" + n);\n\n    }\n\n}\n\n\u8fd0\u884c\u7ed3\u679c\uff1a\n\nThis point is\uff1a10, 20\n\nThis point is\uff1a25.4, \u4e1c\u4eac180\u5ea6<\/code><\/pre>\n
\u7c7b\u540d\u540e\u9762\u7684 <T1, T2><\/code> \u662f\u7c7b\u578b\u53c2\u6570\uff0c\u5360\u4f4d\u7b26\uff0c\u8fd0\u884c\u65f6\u6362\u6210\u771f\u6b63\u7684\u7c7b\u578b\u3002\u4f20\u503c\u53c2\u6570\u7528\u5c0f\u62ec\u53f7\uff0c\u7c7b\u578b\u53c2\u6570\u7528\u5c16\u62ec\u53f7\uff0c\u591a\u4e2a\u7528\u9017\u53f7\u5206\u9694\u3002\u4e60\u60ef\u7528\u5355\u4e2a\u5927\u5199\u5b57\u6bcd\uff1aK<\/code> \u952e\u3001V<\/code> \u503c\u3001E<\/code> \u5f02\u5e38\u6216\u5143\u7d20\u3001T<\/code> \u4e00\u822c\u7c7b\u578b\u3002<\/p>\n
\u6cdb\u578b\u7c7b\u5b9e\u4f8b\u5316<\/h3>\n
\u5b9e\u4f8b\u5316\u5fc5\u987b\u6307\u51fa\u5177\u4f53\u7c7b\u578b\uff08\u5411\u7c7b\u578b\u53c2\u6570\u4f20\u503c\uff09\uff1a<\/p>\n
className variable<dataType1, dataType2> = new className<dataType1, dataType2>();<\/code><\/pre>\n
\u7b49\u53f7\u53f3\u8fb9\u7684\u7c7b\u578b\u53ef\u4ee5\u7701\u7565\uff0c\u4f46\u4f1a\u6709\u8b66\u544a\uff1a<\/p>\n
className variable<dataType1, dataType2> = new className();<\/code><\/pre>\n
\u6307\u660e\u7c7b\u578b\u540e\uff0c\u8d4b\u9519\u7c7b\u578b\u4f1a\u76f4\u63a5\u62a5\u9519\uff0c\u65e2\u4e0d\u5fc5\u5411\u4e0b\u8f6c\u578b\uff0c\u4e5f\u6ca1\u6709\u6f5c\u5728\u7684 ClassCast \u98ce\u9669\uff0c\u6bd4\u4e00\u4e0a\u6765\u5c31\u88c5\u7bb1\u5347 Object \u5b9e\u7528\u3002<\/p>\n\n\n\n\n\n\n\n
\u5199\u6cd5<\/th>\n\u53d6\u51fa\u65f6<\/th>\n\u98ce\u9669<\/th>\n<\/tr>\n<\/thead>\n
Object + \u88c5\u7bb1\/\u5411\u4e0a\u8f6c\u578b<\/td>\n\u5fc5\u987b\u5411\u4e0b\u8f6c\u578b<\/td>\n\u8fd0\u884c\u671f ClassCastException<\/td>\n<\/tr>\n
\u6cdb\u578b\u7c7b Point<\/td>\n\u7f16\u8bd1\u5668\u5df2\u8bb0\u4f4f\u7c7b\u578b<\/td>\n\u8d4b\u9519\u7c7b\u578b\u7f16\u8bd1\u5931\u8d25<\/td>\n<\/tr>\n
\u6cdb\u578b\u4f46\u672a\u4f20\u7c7b\u578b\uff08\u64e6\u9664\uff09<\/td>\n\u4ecd\u8981\u5411\u4e0b\u8f6c\u578b<\/td>\n\u9000\u56de Object \u65b9\u6848<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\u4e09\u3001\u6cdb\u578b\u65b9\u6cd5<\/h2>\n
\u4e5f\u53ef\u4ee5\u53ea\u7ed9\u65b9\u6cd5\u52a0\u7c7b\u578b\u53c2\u6570\u3002\u6253\u5370\u5750\u6807\u7684\u6cdb\u578b\u65b9\u6cd5\uff1a<\/p>\n
\/\/ \u5b9a\u4e49\u6cdb\u578b\u7c7b\n\nclass Point<T1, T2>{\n\n    T1 x;\n\n    T2 y;\n\n    public T1 getX() {\n\n        return x;\n\n    }\n\n    public void setX(T1 x) {\n\n        this.x = x;\n\n    }\n\n    public T2 getY() {\n\n        return y;\n\n    }\n\n    public void setY(T2 y) {\n\n        this.y = y;\n\n    }\n\n\n\n    \/\/ \u5b9a\u4e49\u6cdb\u578b\u65b9\u6cd5\n\n    public <T1, T2> void printPoint(T1 x, T2 y){\n\n        T1 m = x;\n\n        T2 n = y;\n\n       System.out.println(\"This point is\uff1a\" + m + \", \" + n);\n\n    }\n\n}\n\n\n\npublic class Demo {\n\n    public static void main(String[] args){\n\n        \/\/ \u5b9e\u4f8b\u5316\u6cdb\u578b\u7c7b\n\n       Point<Integer, Integer> p1 = new Point<Integer, Integer>();\n\n       p1.setX(10);\n\n       p1.setY(20);\n\n       p1.printPoint(p1.getX(), p1.getY());\n\n\n\n       Point<Double, String> p2 = new Point<Double, String>();\n\n       p2.setX(25.4);\n\n       p2.setY(\"\u4e1c\u4eac180\u5ea6\");\n\n       p2.printPoint(p2.getX(), p2.getY());\n\n    }\n\n}\n\n\u8fd0\u884c\u7ed3\u679c\uff1a\n\nThis point is\uff1a10, 20\n\nThis point is\uff1a25.4, \u4e1c\u4eac180\u5ea6<\/code><\/pre>\n
printPoint()<\/code> \u7684\u7c7b\u578b\u53c2\u6570\u653e\u5728\u4fee\u9970\u7b26\u540e\u9762\u3001\u8fd4\u56de\u503c\u524d\u9762\uff0c\u53ef\u5728\u53c2\u6570\u5217\u8868\u3001\u65b9\u6cd5\u4f53\u3001\u8fd4\u56de\u7c7b\u578b\u91cc\u4f7f\u7528\u3002\u8c03\u7528\u65f6\u4e0d\u5fc5\u624b\u5199\u7c7b\u578b\uff0c\u7f16\u8bd1\u5668\u6839\u636e\u5b9e\u53c2\u63a8\u65ad\u3002\u8c03\u7528\u65b9\u5f0f\u548c\u666e\u901a\u65b9\u6cd5\u4e00\u6837\u3002<\/p>\n
\u6cdb\u578b\u65b9\u6cd5\u4e0e\u6cdb\u578b\u7c7b\u6ca1\u6709\u5fc5\u7136\u8054\u7cfb\uff1a\u666e\u901a\u7c7b\u91cc\u4e5f\u80fd\u5b9a\u4e49\u6cdb\u578b\u65b9\u6cd5\u3002\u65b9\u6cd5\u91cc\u7684 T1\u3001T2 \u548c\u7c7b\u4e0a\u7684 T1\u3001T2 \u4e0d\u662f\u4e00\u56de\u4e8b\uff0c\u53ef\u6362\u6210\u522b\u7684\u6807\u8bc6\uff1a<\/p>\n
public static <V1, V2> void printPoint(V1 x, V2 y){\n\n    V1 m = x;\n\n    V2 n = y;\n\n   System.out.println(\"This point is\uff1a\" + m + \", \" + n);\n\n}<\/code><\/pre>\n
\u56db\u3001\u6cdb\u578b\u63a5\u53e3<\/h2>\n
\u63a5\u53e3\u540c\u6837\u53ef\u4ee5\u5e26\u7c7b\u578b\u53c2\u6570\u3002\u5b9e\u73b0\u7c7b\u8ddf\u4e0a\u76f8\u540c\u7684 T\uff0c\u6784\u9020\u65b9\u6cd5\u4e5f\u53ef\u4ee5\u662f\u6cdb\u578b\u7684\uff1a<\/p>\n
\/\/\u5b9a\u4e49\u6cdb\u578b\u63a5\u53e3\n\ninterface Info<T>{\n\n    public T getVar();\n\n}\n\n\/\/\u5b9e\u73b0\u63a5\u53e3\n\nclass InfoImp<T> implements Info<T> {\n\n    private T var;\n\n    \/\/ \u5b9a\u4e49\u6cdb\u578b\u6784\u9020\u65b9\u6cd5\n\n    public InfoImp(T var) {\n\n       this.setVar(var);\n\n    }\n\n    public void setVar(T var) {\n\n       this.var = var;\n\n    }\n\n    public T getVar() {\n\n        return this.var;\n\n    }\n\n}\n\npublic class Demo {\n\n    public static void main(String arsg[]) {\n\n       Info<String> obj = new InfoImp<String>(\"www.weixueyuan.net\");\n\n       System.out.println(\"Length Of String: \" + obj.getVar().length());\n\n    }\n\n}\n\n\n\n\u8fd0\u884c\u7ed3\u679c\uff1a\n\nLength Of String: 18<\/code><\/pre>\n
\u793a\u4f8b\u7ad9\u70b9\u4ecd\u7528\u539f\u6587 www.weixueyuan.net<\/code>\uff0c\u8f93\u51fa\u5b57\u7b26\u4e32\u957f\u5ea6 18\u3002<\/p>\n
\u4e94\u3001\u7c7b\u578b\u64e6\u9664<\/h2>\n
\u4f7f\u7528\u6cdb\u578b\u65f6\u5982\u679c\u4e0d\u6307\u660e\u6570\u636e\u7c7b\u578b\uff0c\u7f16\u8bd1\u5668\u4f1a\u64e6\u9664\u6cdb\u578b\uff0c\u5168\u90e8\u6309 Object \u5904\u7406\uff0c\u53d6\u51fa\u4ecd\u8981\u5411\u4e0b\u8f6c\u578b\u2014\u2014\u548c\u4e0d\u7528\u6cdb\u578b\u51e0\u4e4e\u4e00\u6837\uff1a<\/p>\n
class Point<T1, T2>{\n\n    T1 x;\n\n    T2 y;\n\n    public T1 getX() {\n\n        return x;\n\n    }\n\n    public void setX(T1 x) {\n\n        this.x = x;\n\n    }\n\n    public T2 getY() {\n\n        return y;\n\n    }\n\n    public void setY(T2 y) {\n\n        this.y = y;\n\n    }\n\n}\n\npublic class Demo {\n\n    public static void main(String[] args){\n\n        Point p = new Point();  \/\/ \u7c7b\u578b\u64e6\u9664\n\n        p.setX(10);\n\n        p.setY(20.8);\n\n        int x = (Integer)p.getX();  \/\/ \u5411\u4e0b\u8f6c\u578b\n\n        double y = (Double)p.getY();\n\n       System.out.println(\"This point is\uff1a\" + x + \", \" + y);\n\n    }\n\n}\n\n\n\n\u8fd0\u884c\u7ed3\u679c\uff1a\n\nThis point is\uff1a10, 20.8<\/code><\/pre>\n
\u516d\u3001\u9650\u5236\u6cdb\u578b\u7684\u53ef\u7528\u7c7b\u578b<\/h2>\n
\u5f88\u591a\u65f6\u5019\u53ea\u5141\u8bb8\u4e00\u90e8\u5206\u7c7b\u578b\u3002\u4f8b\u5982\u53d6\u6570\u7ec4\u6700\u5927\u503c\u65f6\u8981\u7528 doubleValue()<\/code>\uff0c\u90a3\u662f Number \u7684\u65b9\u6cd5\uff0c\u4e0d\u662f\u6240\u6709\u7c7b\u90fd\u6709\uff1a<\/p>\n
public <T> T getMax(T array[]){\n\n    T max = null;\n\n    for(T element : array){\n\n        max = element.doubleValue() > max.doubleValue() ? element : max;\n\n    }\n\n    return max;\n\n}<\/code><\/pre>\n
\u7528 extends<\/code> \u9650\u5236 T \u53ea\u80fd\u662f Number \u53ca\u5176\u5b50\u7c7b\uff08Integer\u3001Double \u7b49\uff09\uff0c\u4f20\u5165\u5176\u5b83\u7c7b\u578b\u4f1a\u62a5\u9519\uff1a<\/p>\n
public <T extends Number> T getMax(T array[]){\n\n    T max = null;\n\n    for(T element : array){\n\n        max = element.doubleValue() > max.doubleValue() ? element : max;\n\n    }\n\n    return max;\n\n}<\/code><\/pre>\n
\u8fd9\u91cc\u7684 extends \u4e0d\u662f\u201c\u7ee7\u627f\u201d\u90a3\u4e2a\u610f\u601d\uff0c\u5e94\u8bfb\u6210\uff1aT \u662f Number \u7684\u5b50\u7c7b\u578b\uff0c\u6216 T \u5b9e\u73b0\u4e86\u67d0\u63a5\u53e3\u3002\u65e5\u5e38\u4e1a\u52a1\u91cc\u6cdb\u578b\u7528\u5f97\u4e0d\u591a\uff0c\u6846\u67b6\u548c\u7c7b\u5e93\u91cc\u624d\u5bc6\u96c6\u51fa\u73b0\uff1b\u5148\u5efa\u7acb\u5370\u8c61\u5373\u53ef\u3002<\/p>\n
\n
\u4e00\u53e5\u8bdd\u603b\u7ed3\uff1a\u6cdb\u578b\u628a\u7c7b\u578b\u4e5f\u53d8\u6210\u53c2\u6570\uff1a\u7f16\u8bd1\u671f\u8bb0\u4f4f T\uff0c\u907f\u514d\u76f2\u76ee\u5411\u4e0b\u8f6c\u578b\uff1b\u4e0d\u5199\u7c7b\u578b\u5c31\u7b49\u4e8e\u64e6\u56de Object\u3002<\/strong><\/p>\n<\/blockquote>\n<\/section>\n","protected":false},"excerpt":{"rendered":"
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