一 用class.forname反射獲取對(duì)象(必須要一個(gè)無(wú)參的構(gòu)造函數(shù))

package com.learing._01;class Student{public Student(){System.out.println("Student類的構(gòu)造方法");}@Overridepublic String toString(){return "Student類的toString()方法";} }public class ReflectDemo {public static void main(String args[]) throws Exception{Class<?> cls = Class.forName("com.learing._01.Student");Object obj = cls.newInstance();}}
輸出結(jié)果

二 獲取構(gòu)造方法

package com.learing._01;import java.lang.reflect.Constructor;public class ReflectStringDemo {public static void main(String args[]) throws Exception{Class<?> cls = Class.forName("java.lang.String");Constructor<?> cons[] = cls.getConstructors();for(int i = 0 ; i < cons.length ; i++){System.out.println(cons[i]);}}}
輸出結(jié)果

三 通過(guò)構(gòu)造方法實(shí)例化對(duì)象

package com.learing._01;import java.lang.reflect.Constructor;class Student {private String name;private Integer age;public Student(String name, Integer age) {this.name = name;this.age = age;}public Student() {}@Overridepublic String toString() {return "Student [name=" + name + ", age=" + age + "]";}}public class ReflectDemo {public static void main(String args[]) throws Exception {Class<?> cls = Class.forName("com.learing._01.Student");Constructor<?> cons = cls.getConstructor(String.class,Integer.class);Object obj = cons.newInstance("SMITH",20);System.out.println(obj.toString());}}
輸出結(jié)果

四 通過(guò)反射獲取方法

此功能用于IDE開發(fā)工具,當(dāng)輸入一“.”時(shí)候,會(huì)出來(lái)該類有哪些方法

package com.learing._01;import java.lang.reflect.Constructor; import java.lang.reflect.Method; import java.lang.reflect.Modifier;interface Message{public void get(); }class Student implements Message{@Overridepublic void get() {}public void print(String name,int age){}public void fun() throws Exception{}}public class ReflectDemo {public static void main(String args[]) throws Exception {Class<?> cls = Class.forName("com.learing._01.Student");Method met[] = cls.getMethods();for(int i = 0 ; i < met.length ; i++){//以下 partA的輸出和partB一樣// partA // System.out.println(met[i]);// partB startSystem.out.print(Modifier.toString(met[i].getModifiers())+" ");//得到修飾符 public final nativeSystem.out.print(met[i].getReturnType().getSimpleName()+" ");//得到返回類型 voidSystem.out.print(met[i].getName()+"("); // 得到方法名 get,printClass<?> params[] = met[i].getParameterTypes(); //得到方法的參數(shù)類型if(params!=null&?ms.length > 0 ){for(int j = 0 ; j < params.length ; j++){System.out.print(params[j].getSimpleName()+""); //取參數(shù)if(j<params.length-1){System.out.print(" , ");}}}System.out.print(") ");Class<?> exceps[] = met[i].getExceptionTypes(); //獲取異常if( exceps!=null && exceps.length>0 ){System.out.print(" throws ");for(int j = 0 ; j < exceps.length ; j++){System.out.print(exceps[j].getSimpleName());if(j < exceps.length -1){System.out.print(", ");}}}System.out.println();// partB end}}}
輸出結(jié)果

五 反射調(diào)用方法

package com.learing._01;import java.lang.reflect.Constructor; import java.lang.reflect.Method; import java.lang.reflect.Modifier;class Student{private String name;public void setName(String name){this.name = name;}public String getName(){return name;} }public class ReflectDemo {public static void main(String args[]) throws Exception{Class<?> cls = Class.forName("com.learing._01.Student");Object obj = cls.newInstance(); //實(shí)例化對(duì)象Method setNameMethod = cls.getMethod("setName", String.class);Method getNameMethod = cls.getMethod("getName");setNameMethod.invoke(obj, "SMITH"); // 對(duì)象.setName("SMITH");System.out.println(getNameMethod.invoke(obj));}}
輸出結(jié)果

六 屬性操作

package com.learing._01;import java.lang.reflect.Constructor; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.lang.reflect.Modifier;interface Message{public static final String INFO = "hello world"; }class Person{private String name;private Integer age; }class Student extends Person implements Message{private String school;private Double price;}public class ReflectDemo {public static void main(String args[]) throws Exception{Class<?> cls = Class.forName("com.learing._01.Student");{ //取得繼承而來(lái)的全部屬性System.out.println();Field fields[] = cls.getFields();System.out.println("繼承而來(lái)的屬性");for(int i = 0 ; i < fields.length ; i++){System.out.println(fields[i]);}}{//取得本類定義的全部屬性System.out.println();Field fields[] = cls.getDeclaredFields();System.out.println("本類定義的全部屬性");for(int i = 0 ; i < fields.length ; i++){System.out.println(fields[i]);}}{//取得父類屬性System.out.println();Field fields[] = cls.getSuperclass().getDeclaredFields(); System.out.println("父類屬性定義的全部屬性");for(int i = 0 ; i < fields.length ; i++){System.out.println(fields[i]);}}{ //操作屬性System.out.println();System.out.println("屬性的操作");Object obj = cls.newInstance();Field schoolField = cls.getDeclaredField("school");schoolField.setAccessible(true);//以為school屬性為private ,setAccessible可以操作該屬性schoolField.set(obj,"清華大學(xué)");System.out.println(schoolField.get(obj));}}}
輸出結(jié)果

總結(jié)

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