JAVA学习--反射构造器操作
1 @Test 2 public void test1() throws Exception{ 3 String className = "com.atguigu.java.Person"; 4 Class clazz = Class.forName(className); 5 //创建对应的运行时类的对象。使用newInstance()，实际上就是调用了运行时类的空参的构造器。 6 //要想能够创建成功：①要求对应的运行时类要有空参的构造器。②构造器的权限修饰符的权限要足够。 7 Object obj = clazz.newInstance(); 8 Person p = (Person)obj; 9 System.out.println(p); 10 }
1 @Test 2 public void test2() throws ClassNotFoundException{ 3 String className = "com.atguigu.java.Person"; 4 Class clazz = Class.forName(className); 5 6 Constructor[] cons = clazz.getDeclaredConstructors(); 7 for(Constructor c : cons){ 8 System.out.println(c); 9 } 10 }
1 //调用指定的构造器,创建运行时类的对象 2 @Test 3 public void test3() throws Exception{ 4 String className = "com.atguigu.java.Person"; 5 Class clazz = Class.forName(className); 6 7 Constructor cons = clazz.getDeclaredConstructor(String.class,int.class); 8 cons.setAccessible(true); 9 Person p = (Person)cons.newInstance("罗伟",20); 10 System.out.println(p); 11 }
1 class Person extends Creature<String> implements Comparable,MyInterface{ 2 public String name; 3 private int age; 4 int id; 5 //创建类时，尽量保留一个空参的构造器。 6 public Person() { 7 super(); 8 // System.out.println("今天天气很闷热"); 9 } 10 public Person(String name) { 11 super(); 12 this.name = name; 13 } 14 private Person(String name, int age) { 15 super(); 16 this.name = name; 17 this.age = age; 18 } 19 public String getName() { 20 return name; 21 } 22 public void setName(String name) { 23 this.name = name; 24 } 25 public int getAge() { 26 return age; 27 } 28 public void setAge(int age) { 29 this.age = age; 30 } 31 32 public int getId() { 33 return id; 34 } 35 public void setId(int id) { 36 this.id = id; 37 } 38 @MyAnnotation(value = "abc123") 39 public void show(){ 40 System.out.println("我是一个人！"); 41 } 42 43 private Integer display(String nation,Integer i) throws Exception{ 44 System.out.println("我的国籍是：" + nation); 45 return i; 46 } 47 @Override 48 public String toString() { 49 return "Person [name=" + name + ", age=" + age + "]"; 50 } 51 @Override 52 public int compareTo(Object o) { 53 // TODO Auto-generated method stub 54 return 0; 55 } 56 57 public static void info(){ 58 System.out.println("中国人！"); 59 } 60 61 class Bird{ 62 63 } 64 65 }
1 import static java.lang.annotation.ElementType.CONSTRUCTOR; 2 import static java.lang.annotation.ElementType.FIELD; 3 import static java.lang.annotation.ElementType.LOCAL_VARIABLE; 4 import static java.lang.annotation.ElementType.METHOD; 5 import static java.lang.annotation.ElementType.PARAMETER; 6 import static java.lang.annotation.ElementType.TYPE; 7 8 import java.lang.annotation.Retention; 9 import java.lang.annotation.RetentionPolicy; 10 import java.lang.annotation.Target; 11 12 @Target({TYPE, FIELD, METHOD, PARAMETER, CONSTRUCTOR, LOCAL_VARIABLE}) 13 @Retention(RetentionPolicy.RUNTIME) 14 public @interface MyAnnotation { 15 String value(); 16 }
1 public class Creature<T>{ 2 public double weight; 3 4 public void breath(){ 5 System.out.println("呼吸！"); 6 } 7 }
1 import java.io.Serializable; 2 3 public interface MyInterface extends Serializable{ 4 5 }
