The Java Tutorials have been written for JDK 8.Java教程是为JDK 8编写的。Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.本页中描述的示例和实践没有利用后续版本中引入的改进，并且可能使用不再可用的技术。See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.有关Java SE 9及其后续版本中更新的语言特性的摘要，请参阅Java语言更改。
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.有关所有JDK版本的新功能、增强功能以及已删除或不推荐的选项的信息，请参阅JDK发行说明。
The Java compiler also erases type parameters in generic method arguments. Java编译器还删除泛型方法参数中的类型参数。Consider the following generic method:考虑下面的泛型方法：
// Counts the number of occurrences of elem in anArray.
//
public static <T> int count(T[] anArray, T elem) {
int cnt = 0;
for (T e : anArray)
if (e.equals(elem))
++cnt;
return cnt;
}Because T is unbounded, the Java compiler replaces it with Object:因为T是无界的，所以Java编译器将其替换为Object：
public static int count(Object[] anArray, Object elem) {
int cnt = 0;
for (Object e : anArray)
if (e.equals(elem))
++cnt;
return cnt;
}Suppose the following classes are defined:假设定义了以下类：
class Shape { /* ... */ }
class Circle extends Shape { /* ... */ }
class Rectangle extends Shape { /* ... */ }You can write a generic method to draw different shapes:您可以编写通用方法来绘制不同的形状：
public static <T extends Shape> void draw(T shape) { /* ... */ }The Java compiler replaces T with Shape:Java编译器将T替换为Shape：
public static void draw(Shape shape) { /* ... */ }