Java: Record

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/**  * 版权所有 2022 涂聚文有限公司  * 许可信息查看：  * 描述：  *  * 历史版本： JDK 17.01  * 2022-09-12 创建者 geovindu  * 2022-09-12 添加 Lambda  * 2022-09-12 修改：date  * 接口类  * 2022-09-12 修改者：Geovin Du  * 生成API帮助文档的指令：  *javadoc - -encoding Utf-8 -d apidoc DuRecord.java  * Interface  * Record  * Annotation  * Enum  * */       package CoreJava.twelfth;   import java.util.*;   /**  *  *  * */ public class DuRecord {       /**      *      *      * */     public record Point(double x, double y)     {         // A custom constructor         public Point() { this(0, 0); }         // A method         public double distanceFromOrigin()         {             return Math.hypot(x, y);         }         // A static field and method         public static Point ORIGIN = new Point();         public static double distance(Point p, Point q)         {             return Math.hypot(p.x - q.x, p.y - q.y);         }     }     /**      *      *      * */     public record PointInTime(double x, double y, Date when) { }     /**      *      *      * */     public record Range(int from, int to)     {         // A compact constructor         public Range         {             if (from > to) // Swap the bounds             {                 int temp = from;                 from = to;                 to = temp;             }         }     }     }

　　

调用：

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// Record             DuRecord.Point pgeovindu =new DuRecord.Point(3, 4);             System.out.println("pgeovindu 坐标: " + pgeovindu.x() + " " + pgeovindu.y());             System.out.println("距离原点: " + pgeovindu.distanceFromOrigin());             // Same computation with static field and method             System.out.println("距离原点: " +  DuRecord.Point.distance( DuRecord.Point.ORIGIN, pgeovindu));               // A mutable record             var ptgeovindu = new  DuRecord.PointInTime(3, 4, new Date());             System.out.println("前: " + ptgeovindu);             ptgeovindu.when().setTime(0);             System.out.println("后: " + ptgeovindu);               // Invoking a compact constructor               var rgeovindu = new  DuRecord.Range(4, 3);             System.out.println("rgeovindu: " + rgeovindu);

　　

输出：

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pgeovindu 坐标: 3.0 4.0 距离原点: 5.0 距离原点: 5.0 前: PointInTime[x=3.0, y=4.0, when=Sun Oct 30 18:45:44 CST 2022] 后: PointInTime[x=3.0, y=4.0, when=Thu Jan 01 08:00:00 CST 1970] rgeovindu: Range[from=3, to=4]