Java List vs ArrayList [英] Java List vs ArrayList
本文介绍了Java List vs ArrayList的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
矢量<对象> x = new Vector< Object>(); // OK
ArrayList< Object> y = new ArrayList< Object>(); // OK
List< Object> zzz = new ArrayList< Object>(); //好的解决了下面的问题,但问题依然存在
List< Object> z = new List< Object>(); //为什么?编译器错误:无法实例化
解决方案
List
是一个接口,有点像C ++中一些带有 = 0
方法的类。
$ b
但 List< ; T>
(或用Java术语来实现它),所以这些引用是赋值兼容的。
As a C++ oldtimer I have managed to solve my problem but I can not wrap my head around the underlying Java mechanisms here:
Vector<Object> x = new Vector<Object>(); // OK
ArrayList<Object> y = new ArrayList<Object>(); // OK
List<Object> zzz = new ArrayList<Object>(); // OK solves problem below but question remains
List<Object> z = new List<Object>(); // WHY? Compiler error: Cannot instantiate
解决方案
List
is an interface, somewhat like a class with some = 0
methods in C++. You can't instantiate it.
But ArrayList<T>
"inherits" List<T>
(or in Java terms, implements it), so those references are assignment-compatible.
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