public class demo1Main1 {
    public static void main(String[] args) throws Exception {
        //獲取Class對(duì)象的三種對(duì)象
        System.out.println("根據(jù)類名：\t" + User.class);
        System.out.println("根據(jù)對(duì)象：\t" + new User().getClass());
        System.out.println("根據(jù)全限定類名：\t" + Class.forName("demo1.User"));
        //常用的方法
        Class<User> userClass = User.class;
        System.out.println("獲取全限定類名：\t" + userClass.getName());
        System.out.println("獲取類名：\t" + userClass.getSimpleName());
        System.out.println("實(shí)例化：\t" + userClass.newInstance());

    }
}

根據(jù)類名： class demo1.User

根據(jù)對(duì)象： class demo1.User

根據(jù)全限定類名： class demo1.User

獲取全限定類名： demo1.User

獲取類名： User

實(shí)例化： User{name='init', age=0}

public String toString() {
    return (isInterface() ? "interface " : (isPrimitive() ? "" : "class "))
        + getName();
}

package com.cry;
public class Test {
    private  class inner{
    }
    public static void main(String[] args) throws ClassNotFoundException {
        //普通類
        System.out.println(Test.class.getSimpleName()); //Test
        System.out.println(Test.class.getName()); //com.cry.Test
        System.out.println(Test.class.getCanonicalName()); //com.cry.Test
        //內(nèi)部類
        System.out.println(inner.class.getSimpleName()); //inner
        System.out.println(inner.class.getName()); //com.cry.Test$inner
        System.out.println(inner.class.getCanonicalName()); //com.cry.Test.inner
        //數(shù)組
        System.out.println(args.getClass().getSimpleName()); //String[]
        System.out.println(args.getClass().getName()); //[Ljava.lang.String;
        System.out.println(args.getClass().getCanonicalName()); //java.lang.String[]
        //我們不能用getCanonicalName去加載類對(duì)象，必須用getName
        //Class.forName(inner.class.getCanonicalName()); 報(bào)錯(cuò)
        Class.forName(inner.class.getName());
    }
}

public class ConstructionTest implements Serializable {
    public static void main(String[] args) throws Exception {
        Class<?> clazz = null;

        //獲取Class對(duì)象的引用
        clazz = Class.forName("com.example.javabase.User");

        //第一種方法，實(shí)例化默認(rèn)構(gòu)造方法，User必須無(wú)參構(gòu)造函數(shù),否則將拋異常
        User user = (User) clazz.newInstance();
        user.setAge(20);
        user.setName("Jack");
        System.out.println(user);

        System.out.println("--------------------------------------------");

        //獲取帶String參數(shù)的public構(gòu)造函數(shù)
        Constructor cs1 =clazz.getConstructor(String.class);
        //創(chuàng)建User
        User user1= (User) cs1.newInstance("hiway");
        user1.setAge(22);
        System.out.println("user1:"+user1.toString());

        System.out.println("--------------------------------------------");

        //取得指定帶int和String參數(shù)構(gòu)造函數(shù),該方法是私有構(gòu)造private
        Constructor cs2=clazz.getDeclaredConstructor(int.class,String.class);
        //由于是private必須設(shè)置可訪問(wèn)
        cs2.setAccessible(true);
        //創(chuàng)建user對(duì)象
        User user2= (User) cs2.newInstance(25,"hiway2");
        System.out.println("user2:"+user2.toString());

        System.out.println("--------------------------------------------");

        //獲取所有構(gòu)造包含private
        Constructor<?> cons[] = clazz.getDeclaredConstructors();
        // 查看每個(gè)構(gòu)造方法需要的參數(shù)
        for (int i = 0; i < cons.length; i++) {
            //獲取構(gòu)造函數(shù)參數(shù)類型
            Class<?> clazzs[] = cons[i].getParameterTypes();
            System.out.println("構(gòu)造函數(shù)["+i+"]:"+cons[i].toString() );
            System.out.print("參數(shù)類型["+i+"]:(");
            for (int j = 0; j < clazzs.length; j++) {
                if (j == clazzs.length - 1)
                    System.out.print(clazzs[j].getName());
                else
                    System.out.print(clazzs[j].getName() + ",");
            }
            System.out.println(")");
        }
    }
}

class User {
    private int age;
    private String name;
    public User() {
        super();
    }
    public User(String name) {
        super();
        this.name = name;
    }

    /**
     * 私有構(gòu)造
     * @param age
     * @param name
     */
    private User(int age, String name) {
        super();
        this.age = age;
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" +
                "age=" + age +
                ", name='" + name + '\'' +
                '}';
    }
}

Constructor cs3 = clazz.getDeclaredConstructor(int.class,String.class);
System.out.println("-----getDeclaringClass-----");
Class uclazz=cs3.getDeclaringClass();
//Constructor對(duì)象表示的構(gòu)造方法的類
System.out.println("構(gòu)造方法的類:"+uclazz.getName());

System.out.println("-----getGenericParameterTypes-----");
//對(duì)象表示此 Constructor 對(duì)象所表示的方法的形參類型
Type[] tps=cs3.getGenericParameterTypes();
for (Type tp:tps) {
    System.out.println("參數(shù)名稱tp:"+tp);
}
System.out.println("-----getParameterTypes-----");
//獲取構(gòu)造函數(shù)參數(shù)類型
Class<?> clazzs[] = cs3.getParameterTypes();
for (Class claz:clazzs) {
    System.out.println("參數(shù)名稱:"+claz.getName());
}
System.out.println("-----getName-----");
//以字符串形式返回此構(gòu)造方法的名稱
System.out.println("getName:"+cs3.getName());

System.out.println("-----getoGenericString-----");
//返回描述此 Constructor 的字符串，其中包括類型參數(shù)。
System.out.println("getoGenericString():"+cs3.toGenericString());

-----getDeclaringClass-----
構(gòu)造方法的類:com.example.javabase.User
-----getGenericParameterTypes-----
參數(shù)名稱tp:int
參數(shù)名稱tp:class java.lang.String
-----getParameterTypes-----
參數(shù)名稱:int
參數(shù)名稱:java.lang.String
-----getName-----
getName:com.example.javabase.User
-----getoGenericString-----
getoGenericString():private com.example.javabase.User(int,java.lang.String)

field:public int reflect.Person.age
f:public java.lang.String reflect.Student.desc
f:public int reflect.Person.age
f:public java.lang.String reflect.Person.name

================getDeclaredFields====================
f2:public java.lang.String reflect.Student.desc
f2:private int reflect.Student.score
field2:public java.lang.String reflect.Student.desc

//獲取Class對(duì)象引用
Class<?> clazz = Class.forName("reflect.Student");

Student st= (Student) clazz.newInstance();
//獲取父類public字段并賦值
Field ageField = clazz.getField("age");
ageField.set(st,18);
Field nameField = clazz.getField("name");
nameField.set(st,"Lily");
//只獲取當(dāng)前類的字段,不獲取父類的字段
Field descField = clazz.getDeclaredField("desc");
descField.set(st,"I am student");
Field scoreField = clazz.getDeclaredField("score");
//設(shè)置可訪問(wèn)，score是private的
scoreField.setAccessible(true);
scoreField.set(st,88);
System.out.println(st.toString());
//輸出結(jié)果：Student{age=18, name='Lily ,desc='I am student', score=88} 
//獲取字段值
System.out.println(scoreField.get(st));
// 88
其中的set(Object obj, Object value) 方法是Field類本身的方法，用于設(shè)置字段的值，而get(Object obj)則是獲取字段的值，當(dāng)然關(guān)于Field類還有其他常用的方法如下：

Class clazz = Class.forName("reflect.Circle");
//創(chuàng)建對(duì)象
Circle circle = (Circle) clazz.newInstance();
//獲取指定參數(shù)的方法對(duì)象Method
Method method = clazz.getMethod("draw",int.class,String.class);
//通過(guò)Method對(duì)象的invoke(Object obj,Object... args)方法調(diào)用
method.invoke(circle,15,"圈圈");
//對(duì)私有無(wú)參方法的操作
Method method1 = clazz.getDeclaredMethod("drawCircle");
//修改私有方法的訪問(wèn)標(biāo)識(shí)
method1.setAccessible(true);
method1.invoke(circle);
//對(duì)有返回值得方法操作
Method method2 =clazz.getDeclaredMethod("getAllCount");
Integer count = (Integer) method2.invoke(circle);
System.out.println("count:"+count);

draw 圈圈,count=15
drawCircle
count:100

public interface Type {
    //1.8新增
    default String getTypeName() {
        return toString();
    }
}