Java 反射常用方法示例
阿新 • • 發佈:2019-01-04
<pre name="code" class="java">import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; class Point{ int x; private int y; public Point(){ x = 1; y = 2; } public void setX(int x) { this.x = x; } public void setY(int y) { this.y = y; } private Point(int x){ this(); this.x = x; } public Point(int x, int y) { super(); this.x = x; this.y = y; } public void printPoint(){ System.out.println("x = " + x + " , y = " + y); } } public class ReflectTest2 { public static void main(String[] args) throws Exception { //使用第一種方法建立物件 Class cls1 = Class.forName("Point"); Constructor con1 = cls1.getConstructor(int.class,int.class); Point p1 = (Point) con1.newInstance(5,6); p1.printPoint(); //使用第二種方法建立物件 Class cls2 = Point.class; Point p2 = (Point) cls2.newInstance();//無參建構函式 p2.printPoint(); //使用第三種方法建立物件 Class cls3 = p1.getClass(); //使用p1物件的setX方法將x值修改為10 Method m1 = cls3.getMethod("setX", int.class); m1.invoke(p1, 10); p1.printPoint(); /* * Note: * getDeclaredConstructor可以返回指定引數的建構函式, * 而getConstructor只能放回指定引數的public的建構函式 * */ Constructor con2 = cls3.getDeclaredConstructor(int.class); //訪問私有變數、函式需要設定accessible con2.setAccessible(true); Point p4 = (Point) con2.newInstance(3); p4.printPoint(); //Field f1 = cls3.getField("y");//error Field f1 = cls3.getDeclaredField("y"); f1.setAccessible(true); //獲取p1的y值 System.out.println(f1.get(p1)); } }