Java 8 样本未返回预期输出 'Test Passed'

Question

我是 Java 8 的新手，我正在尝试使用 lambda 表达式创建示例程序

我想在 driver.getTitle() 方法 returns "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 工作流程，它在控制台中正确打印输出 'Test Passed'。但是方法 2，使用 Java 8 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");
};

Answer 1

创建实例后，您仍然需要调用自定义功能接口的方法。既然你没有 post 你的 GetTitle class，我将举一个小例子说明它应该如何使用另一个自定义功能接口工作。

// 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.
}

我希望这能让您对函数式接口的工作原理有足够的了解。

Answer 2

您必须声明一个 GetTitle 接口并调用该接口内的方法。

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 class 内部或 class 外部。

Java 8 样本未返回预期输出 'Test Passed'

The expected output 'Test Passed' is not returned for the Java 8 Sample

java

implementation