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