【Java8 新特性 4】java8 optional

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从 Java 8 引入的一个很有趣的特性是 Optional  类。Optional 类主要解决的问题是臭名昭著的空指针异常(NullPointerException) —— 每个 Java 程序员都非常了解的异常。

本质上,这是一个包含有可选值的包装类,这意味着 Optional 类既可以含有对象也可以为空。

Optional 是 Java 实现函数式编程的强劲一步,并且帮助在范式中实现。但是 Optional 的意义显然不止于此。

我们从一个简单的用例开始。在 Java 8 之前,任何访问对象方法或属性的调用都可能导致 NullPointerException:

package test.optional;

public class School {
	private Teacher teacher;

	public Teacher getTeacher() {
		return te
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