java泛型(外国英语资料).docVIP

java泛型(国外英语资料) English original address: Http:///pub/a/onjava/2005/07/06/generics.html Chinese address: Http:///resource/article/43/43634_java_generics.html Keywords: Java, generics, java5 abstract Generics are the most important feature of J2SE 5. They let you write a type (class or interface) and create an instance by passing one or more reference types. This instance is limited to these types only. For example, in Java 5, java.util.List has been generalized. When you build a list object, you build a List instance by passing a Java type, and this list instance can only work on the type passed. This means that if you pass a String, this List instance can only have String objects; if you pass a Integer, this instance can only store Integer objects. In addition to creating parameterized types, you can also create parameterized functions. The first benefit of generics is strict type checking at compile time. This is the most important feature of the collection framework. In addition, generics eliminate most types of transformations. Before JDK 5, when you were using a collection framework, you had to type conversions. This article will show you how to manipulate generics. The first part of it is no generic days, lets recall the inconvenience of the old version of JDK first. Then, give some examples of generics. After discussing syntax and the use of bounded generics, the last chapter of the article will explain how to write generics. Days without generics All Java classes are derived from java.lang.Object, which means that all JAVA objects can be converted to Object. Thus, in the previous version of JDK, many collection framework functions accepted a Object parameter. So, collections is a utility tool that holds any object, but it has bad consequences. For a simple example, in the previous version of JDK 5, the class List function add accepts a Object parameter: Public Boolean add (java.lang.Object element) So you can pass any type to add. It was purposely designed. O