fix example code (#403)

* 忽路->忽略

* 修复跳转链接错误

* fix Class.getInterface() -> Class.getInterfaces()

* 否者 -> 否则

* 编译期 -> 编译器 ，原文"the compiler will only allow you to say that the superclass reference is “some class that is a superclass of FancyToy” a"

* ierator -> iterator

* nextint -> nextInt

* fix 这句翻译第一反应没太看懂，结合原文和下面的例子优化了一下翻译

* fix ojb -> obj

* fix example code

docs/book/20-Generics.md

@@ -1595,7 +1595,7 @@ import java.util.function.*;
 import onjava.*;
 
 public class FilledList<T> extends ArrayList<T> {
-    FilledList<Supplier<T> gen, int size) {
+    FilledList(Supplier<T> gen, int size) {
         Suppliers.fill(this, gen, size);
     }