Java接口-它们的作用是什么？

接口允许您在运行时提供不同的实现，注入依赖项，单独的关注点，使用不同的实现进行测试。

只需将接口视为类保证实现的契约即可。实现该接口的具体类无关紧要。不知道这是否有帮助。

想出一些代码可能会有所帮助。这并不能解释界面的所有内容，请继续阅读，但我希望这可以帮助您入门。这里的重点是您可以更改实现…

package stack.overflow.example;public interface IExampleService {void callExpensiveService();}public class TestService implements IExampleService {@Overridepublic void callExpensiveService() {    // This is a mock service, we run this as many     // times as we like for free to test our software}}public class ExpensiveService implements IExampleService {@Overridepublic void callExpensiveService() {    // This performs some really expensive service,    // Ideally this will only happen in the field    // We'd rather test as much of our software for    // free if possible.}}public class Main {public static void main(String[] args) {    // In a test program I might write    IExampleService testService = new TestService();    testService.callExpensiveService();    // Alternatively, in a real program I might write    IExampleService testService = new ExpensiveService();    testService.callExpensiveService();    // The difference above, is that we can vary the concrete     // class which is instantiated. In reality we can use a     // service locator, or use dependency injection to determine     // at runtime which class to implement.    // So in the above example my testing can be done for free, but     // real world users would still be charged. Point is that the interface    // provides a contract that we know will always be fulfilled, regardless     // of the implementation.}}