{"id":115,"date":"2015-03-31T17:46:08","date_gmt":"2015-03-31T09:46:08","guid":{"rendered":"https:\/\/ai.zhousir.top\/?p=115"},"modified":"2016-03-02T17:31:20","modified_gmt":"2016-03-02T09:31:20","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":"

\u672c\u8282\u5148\u8bb2\u89e3\u5982\u4f55\u9650\u5236\u7c7b\u578b\u53c2\u6570\u7684\u8303\u56f4\uff0c\u518d\u8bb2\u89e3\u901a\u914d\u7b26(?)\u3002
\n\u7c7b\u578b\u53c2\u6570\u7684\u8303\u56f4
\n\u5728\u6cdb\u578b\u4e2d\uff0c\u5982\u679c\u4e0d\u5bf9\u7c7b\u578b\u53c2\u6570\u52a0\u4ee5\u9650\u5236\uff0c\u5b83\u5c31\u53ef\u4ee5\u63a5\u53d7\u4efb\u610f\u7684\u6570\u636e\u7c7b\u578b\uff0c\u53ea\u8981\u5b83\u662f\u88ab\u5b9a\u4e49\u8fc7\u7684\u3002\u4f46\u662f\uff0c\u5f88\u591a\u65f6\u5019\u6211\u4eec\u53ea\u9700\u8981\u4e00\u90e8\u5206\u6570\u636e\u7c7b\u578b\u5c31\u591f\u4e86\uff0c\u7528\u6237\u4f20\u9012\u5176\u4ed6\u6570\u636e\u7c7b\u578b\u53ef\u80fd\u4f1a\u5f15\u8d77\u9519\u8bef\u3002\u4f8b\u5982\uff0c\u7f16\u5199\u4e00\u4e2a\u6cdb\u578b\u51fd\u6570\u7528\u4e8e\u8fd4\u56de\u4e0d\u540c\u7c7b\u578b\u6570\u7ec4\uff08Integer \u6570\u7ec4\u3001Double \u6570\u7ec4\u7b49\uff09\u4e2d\u7684\u6700\u5927\u503c\uff1a
\n<\/p>\n

[java]public <T> T getMax(T array[]){
\n\u00a0\u00a0\u00a0 T max = null;
\n\u00a0\u00a0\u00a0 for(T element : array){
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 max = element.doubleValue() > max.doubleValue() ? element : max;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 return max;
\n}[\/java]<\/p>\n

\u4e0a\u9762\u7684\u4ee3\u7801\u4f1a\u62a5\u9519\uff0cdoubleValue() \u662f Number \u7c7b\u53ca\u5176\u5b50\u7c7b\u7684\u65b9\u6cd5\uff0c\u4e0d\u662f\u6240\u6709\u7684\u7c7b\u90fd\u6709\u8be5\u65b9\u6cd5\uff0c\u6240\u4ee5\u6211\u4eec\u8981\u9650\u5236\u7c7b\u578b\u53c2\u6570T\uff0c\u8ba9\u5b83\u53ea\u80fd\u63a5\u53d7 Number \u53ca\u5176\u5b50\u7c7b\uff08Integer\u3001Double\u3001Character \u7b49\uff09\u3002
\n\u901a\u8fc7 extends \u5173\u952e\u5b57\u53ef\u4ee5\u9650\u5236\u6cdb\u578b\u7684\u7c7b\u578b\u7684\u4e0a\u9650\uff0c\u6539\u8fdb\u4e0a\u9762\u7684\u4ee3\u7801\uff1a<\/p>\n

[java]public <T extends Number> T getMax(T array[]){
\n\u00a0\u00a0\u00a0 T max = null;
\n\u00a0\u00a0\u00a0 for(T element : array){
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 max = element.doubleValue() > max.doubleValue() ? element : max;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 return max;
\n}[\/java]<\/p>\n

\u8868\u793a T \u53ea\u63a5\u53d7 Number \u53ca\u5176\u5b50\u7c7b\uff0c\u4f20\u5165\u5176\u4ed6\u7c7b\u578b\u7684\u6570\u636e\u4f1a\u62a5\u9519\u3002\u8fd9\u91cc\u7684\u9650\u5b9a\u4f7f\u7528\u5173\u952e\u5b57extends\uff0c\u540e\u9762\u53ef\u4ee5\u662f\u7c7b\u4e5f\u53ef\u4ee5\u662f\u63a5\u53e3\u3002\u5982\u679c\u662f\u7c7b\uff0c\u53ea\u80fd\u6709\u4e00\u4e2a\uff1b\u4f46\u662f\u63a5\u53e3\u53ef\u4ee5\u6709\u591a\u4e2a\uff0c\u5e76\u4ee5\u201c&\u201d\u5206\u9694\uff0c\u4f8b\u5982 \u3002
\n\u8fd9\u91cc\u7684 extends \u5173\u952e\u5b57\u5df2\u4e0d\u518d\u662f\u7ee7\u627f\u7684\u542b\u4e49\u4e86\uff0c\u5e94\u8be5\u7406\u89e3\u4e3aT \u662f\u7ee7\u627f\u81ea Number \u7c7b\u7684\u7c7b\u578b\uff0c\u6216\u8005 T \u662f\u5b9e\u73b0\u4e86 XX \u63a5\u53e3\u7684\u7c7b\u578b\u3002
\n\u901a\u914d\u7b26(?)
\n\u4e0a\u4e00\u8282\u7684\u4f8b\u5b50\u4e2d\u63d0\u5230\u8981\u5b9a\u4e49\u4e00\u4e2a\u6cdb\u578b\u7c7b\u6765\u8868\u793a\u5750\u6807\uff0c\u5750\u6807\u53ef\u4ee5\u662f\u6574\u6570\u3001\u5c0f\u6570\u6216\u5b57\u7b26\u4e32\uff0c\u8bf7\u770b\u4e0b\u9762\u7684\u4ee3\u7801\uff1a<\/p>\n

[java]class Point<T1, T2>{
\n\u00a0\u00a0\u00a0 T1 x;
\n\u00a0\u00a0\u00a0 T2 y;
\n\u00a0\u00a0\u00a0 public T1 getX() {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return x;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 public void setX(T1 x) {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 this.x = x;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 public T2 getY() {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return y;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 public void setY(T2 y) {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 this.y = y;
\n\u00a0\u00a0\u00a0 }
\n}[\/java]<\/p>\n

\u73b0\u5728\u8981\u6c42\u5728\u7c7b\u7684\u5916\u90e8\u5b9a\u4e49\u4e00\u4e2aprintPoint() \u65b9\u6cd5\u7528\u4e8e\u8f93\u51fa\u5750\u6807\uff0c\u600e\u4e48\u529e\u5462\uff1f
\n\u53ef\u4ee5\u8fd9\u6837\u6765\u5b9a\u4e49\u65b9\u6cd5\uff1a
\n[java]public void printPoint(Point p){
\n System.out.println("This point is: " + p.getX() + ", " + p.getY());
\n}[\/java]
\n\u6211\u4eec\u77e5\u9053\uff0c\u5982\u679c\u5728\u4f7f\u7528\u6cdb\u578b\u65f6\u6ca1\u6709\u6307\u540d\u5177\u4f53\u7684\u6570\u636e\u7c7b\u578b\uff0c\u5c31\u4f1a\u64e6\u9664\u6cdb\u578b\u7c7b\u578b\uff0c\u5e76\u5411\u4e0a\u8f6c\u578b\u4e3aObject\uff0c\u8fd9\u4e0e\u4e0d\u4f7f\u7528\u6cdb\u578b\u6ca1\u4ec0\u4e48\u4e24\u6837\u3002\u4e0a\u9762\u7684\u4ee3\u7801\u6ca1\u6709\u6307\u660e\u6570\u636e\u7c7b\u578b\uff0c\u76f8\u5f53\u4e8e\uff1a
\n[java]public void printPoint(Point&lt;Object, Object&gt; p){
\n System.out.println("This point is: " + p.getX() + ", " + p.getY());
\n}[\/java]
\n\u4e3a\u4e86\u907f\u514d\u7c7b\u578b\u64e6\u9664\uff0c\u53ef\u4ee5\u4f7f\u7528\u901a\u914d\u7b26(?)\uff1a
\n[java]public void printPoint(Point<\/p>\n

<!–?,?–>p){
\nSystem.out.println("This point is: " + p.getX() + ", " + p.getY());
\n}[\/java]
\n\u901a\u914d\u7b26(?)\u53ef\u4ee5\u8868\u793a\u4efb\u610f\u7684\u6570\u636e\u7c7b\u578b\u3002\u5c06\u4ee3\u7801\u8865\u5145\u5b8c\u6574\uff1a<\/p>\n

[java]public class Demo {
\n\u00a0\u00a0\u00a0 public static void main(String[] args){
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Point<Integer, Integer> p1 = new Point<Integer, Integer>();
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 p1.setX(10);
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 p1.setY(20);
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 printPoint(p1);
\n\u00a0\u00a0\u00a0\u00a0\u00a0
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Point<String, String> p2 = new Point<String, String>();
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 p2.setX("\u4e1c\u4eac180\u5ea6");
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 p2.setY("\u5317\u7eac210\u5ea6");
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 printPoint(p2);
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0
\n\u00a0\u00a0\u00a0 public static void printPoint(Point<?, ?> p){ \/\/ \u4f7f\u7528\u901a\u914d\u7b26
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 System.out.println("This point is: " + p.getX() + ", " + p.getY());
\n\u00a0\u00a0\u00a0 }
\n}
\nclass Point<T1, T2>{
\n\u00a0\u00a0\u00a0 T1 x;
\n\u00a0\u00a0\u00a0 T2 y;
\n\u00a0\u00a0\u00a0 public T1 getX() {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return x;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 public void setX(T1 x) {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 this.x = x;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 public T2 getY() {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return y;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 public void setY(T2 y) {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 this.y = y;
\n\u00a0\u00a0\u00a0 }
\n}
\n\u8fd0\u884c\u7ed3\u679c\uff1a
\nThis point is: 10, 20
\nThis point is: \u4e1c\u4eac180\u5ea6, \u5317\u7eac210\u5ea6[\/java]<\/p>\n

\u4f46\u662f\uff0c\u6570\u5b57\u5750\u6807\u4e0e\u5b57\u7b26\u4e32\u5750\u6807\u53c8\u6709\u533a\u522b\uff1a\u6570\u5b57\u53ef\u4ee5\u8868\u793ax\u8f74\u6216y\u8f74\u7684\u5750\u6807\uff0c\u5b57\u7b26\u4e32\u53ef\u4ee5\u8868\u793a\u5730\u7403\u7ecf\u7eac\u5ea6\u3002\u73b0\u5728\u53c8\u8981\u6c42\u5b9a\u4e49\u4e24\u4e2a\u65b9\u6cd5\u5206\u522b\u5904\u7406\u4e0d\u540c\u7684\u5750\u6807\uff0c\u4e00\u4e2a\u65b9\u6cd5\u53ea\u80fd\u63a5\u53d7\u6570\u5b57\u7c7b\u578b\u7684\u5750\u6807\uff0c\u53e6\u4e00\u4e2a\u65b9\u6cd5\u53ea\u80fd\u63a5\u53d7\u5b57\u7b26\u4e32\u7c7b\u578b\u7684\u5750\u6807\uff0c\u600e\u4e48\u529e\u5462\uff1f
\n\u8fd9\u4e2a\u95ee\u9898\u7684\u5173\u952e\u662f\u8981\u9650\u5236\u7c7b\u578b\u53c2\u6570\u7684\u8303\u56f4\uff0c\u8bf7\u5148\u770b\u4e0b\u9762\u7684\u4ee3\u7801\uff1a<\/p>\n

[java]public class Demo {
\n\u00a0\u00a0\u00a0 public static void main(String[] args){
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Point<Integer, Integer> p1 = new Point<Integer, Integer>();
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 p1.setX(10);
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 p1.setY(20);
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 printNumPoint(p1);
\n\u00a0\u00a0\u00a0\u00a0\u00a0
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Point<String, String> p2 = new Point<String, String>();
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 p2.setX("\u4e1c\u4eac180\u5ea6");
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 p2.setY("\u5317\u7eac210\u5ea6");
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 printStrPoint(p2);
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0
\n\u00a0\u00a0\u00a0 \/\/ \u501f\u52a9\u901a\u914d\u7b26\u9650\u5236\u6cdb\u578b\u7684\u8303\u56f4
\n\u00a0\u00a0\u00a0 public static void printNumPoint(Point<? extends Number, ? extends Number> p){
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 System.out.println("x: " + p.getX() + ", y: " + p.getY());
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0
\n\u00a0\u00a0\u00a0 public static void printStrPoint(Point<? extends String, ? extends String> p){
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 System.out.println("GPS: " + p.getX() + "\uff0c" + p.getY());
\n\u00a0\u00a0\u00a0 }
\n}
\nclass Point<T1, T2>{
\n\u00a0\u00a0\u00a0 T1 x;
\n\u00a0\u00a0\u00a0 T2 y;
\n\u00a0\u00a0\u00a0 public T1 getX() {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return x;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 public void setX(T1 x) {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 this.x = x;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 public T2 getY() {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return y;
\n\u00a0\u00a0\u00a0 }
\n\u00a0\u00a0\u00a0 public void setY(T2 y) {
\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 this.y = y;
\n\u00a0\u00a0\u00a0 }
\n}
\n\u8fd0\u884c\u7ed3\u679c\uff1a
\nx: 10, y: 20
\nGPS: \u4e1c\u4eac180\u5ea6\uff0c\u5317\u7eac210\u5ea6[\/java]<\/p>\n

? extends Number \u8868\u793a\u6cdb\u578b\u7684\u7c7b\u578b\u53c2\u6570\u53ea\u80fd\u662fNumber \u53ca\u5176\u5b50\u7c7b\uff0c? extends String \u4e5f\u4e00\u6837\uff0c\u8fd9\u4e0e\u5b9a\u4e49\u6cdb\u578b\u7c7b\u6216\u6cdb\u578b\u65b9\u6cd5\u65f6\u9650\u5236\u7c7b\u578b\u53c2\u6570\u7684\u8303\u56f4\u7c7b\u4f3c\u3002
\n\u4e0d\u8fc7\uff0c\u4f7f\u7528\u901a\u914d\u7b26(?)\u4e0d\u4f46\u53ef\u4ee5\u9650\u5236\u7c7b\u578b\u7684\u4e0a\u9650\uff0c\u8fd8\u53ef\u4ee5\u9650\u5236\u4e0b\u9650\u3002\u9650\u5236\u4e0b\u9650\u4f7f\u7528super \u5173\u952e\u5b57\uff0c\u4f8b\u5982 <? super Number> \u8868\u793a\u53ea\u80fd\u63a5\u53d7 Number \u53ca\u5176\u7236\u7c7b\u3002
\n\u6ce8\u610f\uff1a\u4e00\u822c\u7684\u9879\u76ee\u4e2d\u5f88\u5c11\u4f1a\u53bb\u8bbe\u8ba1\u6cdb\u578b\uff0c\u8fd9\u91cc\u4e3b\u8981\u662f\u8ba9\u8bfb\u8005\u5b66\u4f1a\u5982\u4f55\u4f7f\u7528\uff0c\u4e3a\u540e\u9762\u7684\u6559\u7a0b\u505a\u94fa\u57ab\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"

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