functional interface

更优雅

案例

要在TodoTaskRepository写find方法找到对应task列表，传入自定义的如何find

要传入两个参数，返回一个bool，在文档里找这样的functional interface
java8官方文档-Package java.util.function
BiPredicate是这样的

接口函数是test

public class TodoTaskRepository {
    
    
    private final List<TodoTask> tasks;
		 
		 public <T> List<TodoTask> find(T field, BiPredicate<T,TodoTask> filter) {
    
    
		        var tasksFound = new ArrayList<TodoTask>();
		        for (final TodoTask task : tasks) {
    
    
		            if(filter.test(field, task)) {
    
    
		                tasksFound.add(task);
		            }
		        }
		        return tasksFound;
		    }
}

单元测试

在find传入的参数中直接实现了接口函数test：(field, task) -> field.equals(task.getID())
|| (field,task)->field.equals(task.getStatus())

			@ParameterizedTest
            @ValueSource(ints = {
    
    1, 2, 3, 4, 5})
            public void should_return_task_by_given_id(int givenId) {
    
    
                // Given
                final var todoTaskRepository = new TodoTaskRepository(this.allTasks);
                // When
                final var taskListFound = todoTaskRepository
                							.find(givenId, ((field, task) -> field.equals(task.getID())));
                // Then
                assertTrue(taskListFound.size() > 0);
                for (final TodoTask taskFound : taskListFound) {
    
    
                    assertEquals(givenId, taskFound.getID());
                }
            }

			@ParameterizedTest
            @EnumSource(TodoTaskStatus.class)
            public void should_return_task_by_given_status(TodoTaskStatus givenStatus) {
    
    
                // Given
                final var todoTaskRepository = new TodoTaskRepository(this.allTasks);
                // When
                final var taskListFound = todoTaskRepository
                					     	.find(givenStatus, (field,task)->field.equals(task.getStatus()));
                // Then
                assertNotNull(taskListFound);
                assertTrue(taskListFound.size() > 0);
                for (final TodoTask taskFound : taskListFound) {
    
    
                    assertEquals(givenStatus, taskFound.getStatus());
                }
            }