依赖注入框架Guice使用的简单例子

在Spring Boot实战一书中提到Spring可以更换依赖注入的框架，比如Google的Guice，所以了解一下Hello World怎么写

maven引入依赖

        <dependency>
            <groupId>com.google.inject</groupId>
            <artifactId>guice</artifactId>
            <version>4.2.2</version>
        </dependency>

代码：

/*
 * Sample.java -- JDK 1.8
 */
package com.example.helloguice;

import com.google.inject.Guice;
import com.google.inject.Inject;
import com.google.inject.Injector;
import com.google.inject.Singleton;

@Singleton
public class Sample {
    @Inject // Guice注入实现类的注解
    private HelloPrinter printer;

    public void hello() {
        printer.print();
    }

    public static void main(String[] args) throws InterruptedException {
        Injector injector = Guice.createInjector(); // 创建一个注射器
        Sample sample = injector.getInstance(Sample.class);
        System.out.println("Injecting...");
        Thread.sleep(1000);
        sample.hello();
    }
}

@Singleton
class HelloPrinter {
    public void print() {
        System.out.println("Hello, World!");
    }
}