预期输出'；测试通过'；对于Java8示例，没有返回

我对Java8非常陌生，我正在尝试使用lambda表达式创建一个示例程序

我想在driver.getTitle（）方法返回“Home Page-Safe2Pay Application”时打印“Test Passed”

我实施了两种不同的方法。方法1是正常的Java工作流，它在控制台中正确地打印输出“测试通过”。 但是使用Java8的方法2不起作用

String expectedTitle = "Home Page - Safe2Pay Application";
String actualTitle = "";

//Approach 1
actualTitle = driver.getTitle();

if (actualTitle.contentEquals(expectedTitle)) {
    System.out.println("Test Passed");
} else {
    System.out.println("Test Failed");
}

//Approach 2
//Java 8 execution
GetTitle m = () -> {
    if (driver.getTitle().contentEquals(expectedTitle))
        System.out.println("Test Passed");
    else
        System.out.println("Test Failed");
};

---

创建实例后，仍然需要调用自定义函数接口的方法。由于您没有发布GetTitle类，因此我将给出一个小示例，说明如何使用另一个自定义函数接口工作

// the functional interface
@FunctionalInterface
public static interface Operator {
    public void operate();
}

public static void main(String[] args)
{
    Operator o = () -> System.out.println("test"); //here you create a class instance of Operator.
    o.operate(); // this is how you call that method/functional interface.

    // this is a non-lambda example which works exactually the same, but may make things a bit more clear.

    //create new instance
    Operator o1 = new Operator() {
        @Override
        public void operate()
        {
            System.out.println("test");
        }
    };

    o1.operate(); //call the method.
}

public class Driver {
   static String expectedTitle = "Home Page - Safe2Pay Application";
   static String actualTitle = "";
   public static void main(String args[]){

      Driver driver = new Driver();

      //Approach 1
      actualTitle = getTitle();

      if (actualTitle.contentEquals(expectedTitle)) {
        System.out.println("Test Passed");
      } else {
        System.out.println("Test Failed");
      }

      //Approach 2
      //Java 8 execution
      GetTitle m = (Driver dr) -> {
        if (Driver.getTitle().contentEquals(expectedTitle))
            System.out.println("Test Passed");
        else
            System.out.println("Test Failed");
      };

       m.operation(driver);

    }
    public static String getTitle(){
       return expectedTitle;
    }

   interface GetTitle {
      void operation(Driver driver);
   }
}

---

我希望这能让您充分了解函数接口的工作原理。

您必须声明一个GetTitle接口并调用该接口内的方法

// the functional interface
@FunctionalInterface
public static interface Operator {
    public void operate();
}

public static void main(String[] args)
{
    Operator o = () -> System.out.println("test"); //here you create a class instance of Operator.
    o.operate(); // this is how you call that method/functional interface.

    // this is a non-lambda example which works exactually the same, but may make things a bit more clear.

    //create new instance
    Operator o1 = new Operator() {
        @Override
        public void operate()
        {
            System.out.println("test");
        }
    };

    o1.operate(); //call the method.
}

public class Driver {
   static String expectedTitle = "Home Page - Safe2Pay Application";
   static String actualTitle = "";
   public static void main(String args[]){

      Driver driver = new Driver();

      //Approach 1
      actualTitle = getTitle();

      if (actualTitle.contentEquals(expectedTitle)) {
        System.out.println("Test Passed");
      } else {
        System.out.println("Test Failed");
      }

      //Approach 2
      //Java 8 execution
      GetTitle m = (Driver dr) -> {
        if (Driver.getTitle().contentEquals(expectedTitle))
            System.out.println("Test Passed");
        else
            System.out.println("Test Failed");
      };

       m.operation(driver);

    }
    public static String getTitle(){
       return expectedTitle;
    }

   interface GetTitle {
      void operation(Driver driver);
   }
}

---

接口可以在类内部，也可以在类外部。

方法2只是一个函数定义，但您没有执行它。

GetTitle是什么？

？当您使用lambda时，您基本上保存了一个方法供以后调用。通常会使用另一个方法调用该方法，如

apply（）

或

run（）

或其他方法，具体取决于存储该方法的类型。它可能有助于修复键入错误，以便读者可以自己运行该方法

FunctionInterface

以大写字母

F

开头，您在第2行拼错了

运算符。谢谢，我们会解决它的。当你在移动设备上工作时的打字错误：不要责怪开发者，我完全有能力在任何键盘上做出打字错误。