反射与泛型--使用泛型反射API打印出给定类的所有内容

package chapter8Demos;

import java.lang.reflect.*;
import java.util.Arrays;
import java.util.Scanner;
import source.*;
public class GenericReflectionTest {

    public static void main(String[] args) {
        String name;
        if (args.length > 0) {
            name = args[0];
        }
        else {
            try (Scanner in = new Scanner(System.in)){
                System.out.println("Enter class name (e.g. java.util.Collections): ");
                name = in.next();
            }
        }
        //反射手动输入的这个类
        try {
            Class<?> cl = Class.forName(name);
            //输出类的信息
            printClass(cl);
            for (Method m : cl.getDeclaredMethods()) {
                printMethod(m);
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }

    }
    //输出关于类的信息
    public static void printClass(Class<?> cl) {
        System.out.print(cl);
        //输出泛型
        printTypes(cl.getTypeParameters(),"<",",",">",true);
        //输出父类
        Type sc = cl.getGenericSuperclass();
        if (sc != null) {
            System.out.print(" extends ");
            printType(sc,false);
        }
        //输出实现的接口
        printTypes(cl.getGenericInterfaces()," implements ",", ","",false);
        System.out.println();
    }
    //输出类中定义的方法
    public static void printMethod(Method m) {
        String name = m.getName();
        //Modifier 修饰语
        System.out.print(Modifier.toString(m.getModifiers()));
        System.out.print(" ");
        printTypes(m.getTypeParameters(), "<", ",", ">", true);

        printType(m.getGenericReturnType(), false);
        System.out.print(" ");
        System.out.print(name);
        System.out.print("(");
        printTypes(m.getGenericParameterTypes(), "", ", ", "", false);
        System.out.println(")");
    }
    private static void printType(Type type, boolean isDefinition) {
        if (type instanceof Class) {
            Class<?> t = (Class<?>) type;
            System.out.print(t.getName());
        }
        //描述类型变量
        else if(type instanceof TypeVariable) {
            TypeVariable<?> t = (TypeVariable<?>) type;
            System.out.print(t.getName());
            if (isDefinition) {
                //getBounds获取类型变量的上边界, 若未明确声明上边界则默认为Object
                printTypes(t.getBounds(), " extends ", " & ", "", false);
            }
        }
        //wildcard 通配符
        else if (type instanceof WildcardType) {
            WildcardType t = (WildcardType) type;
            System.out.print("?");
            printTypes(t.getUpperBounds(), " extends ", " & ", "", false);
            printTypes(t.getLowerBounds(), " super ", " & ", "", false);
        }
        //描述泛型类或接口类型
        else if (type instanceof ParameterizedType) {
            ParameterizedType t = (ParameterizedType) type;
            Type owner = t.getOwnerType();
            if (owner != null) {
                printType(owner, false);
                System.out.print(".");
            }
            printType(t.getRawType(), false);
            printTypes(t.getActualTypeArguments(), "<", ",", ">", false);
        }
        //描述泛型数组
        else if (type instanceof GenericArrayType) {
            GenericArrayType t = (GenericArrayType) type;
            System.out.print("");
            printType(t.getGenericComponentType(),isDefinition);
            System.out.print("[]");
        }
    }
    //通用打印，可以处理继承、接口、参数的打印
    //isDefinition输入true则表明该参数变量已经打印完全了，输入false则表明该参数变量还可以被打印的更准确
    private static void printTypes(Type[] types, String pre, String sep, String suf,
            boolean isDefinition) {
        if (pre.equals(" extends ") && Arrays.equals(types, new Type[] {Object.class})) {
            return ;
        }
        if (types.length > 0) {
            System.out.print(pre);
        }
        //顺序打印
        for (int i = 0; i < types.length; i++) {
            if (i > 0) {
                System.out.print(sep);
            }
            printType(types[i], isDefinition);
        }
        if (types.length > 0) {
            System.out.print(suf);
        }
    }
}

JAVA核心技术8-4