lambda

问题 I have two entities with one to many relationship which are joined together by composite primary keys. Since Spring Data generates wrong count distinct query for oracle database , I have SQL output with cartesian join which leads to repeating row for parent object for every row of child object. I need to find out distinct parent objects based on composite keys and then add each child object for parent in a list and set it as property of parent object I am able to find out distinct parent

问题 how could I set my object to another in lambda expression? I got error variable used in lambda expression should be final or effectively final with following code: public MyObj myFun(MyObj o) { MyObj obj = null; myObjList.stream().filter(o -> ...).forEach(o -> { // I do some stuff here // I need here set obj to o, but I got error obj = o; }); return myObj; // I need return found obj or null; } 回答1: You can't assign o to the outer variable. But you can return it as a result of you stream

问题 how could I set my object to another in lambda expression? I got error variable used in lambda expression should be final or effectively final with following code: public MyObj myFun(MyObj o) { MyObj obj = null; myObjList.stream().filter(o -> ...).forEach(o -> { // I do some stuff here // I need here set obj to o, but I got error obj = o; }); return myObj; // I need return found obj or null; } 回答1: You can't assign o to the outer variable. But you can return it as a result of you stream

问题 I'm trying to solve a problem for a course in Python and found someone has implemented solutions for the same problem in github. I'm just trying to understand the solution given in github. I have a pandas dataframe called Top15 with 15 countries and one of the columns in the dataframe is 'HighRenew'. This column stores the % of renewable energy used in each country. My task is to convert the column values in 'HighRenew' column into boolean datatype. If the value for a particular country is

问题 I'm trying to solve a problem for a course in Python and found someone has implemented solutions for the same problem in github. I'm just trying to understand the solution given in github. I have a pandas dataframe called Top15 with 15 countries and one of the columns in the dataframe is 'HighRenew'. This column stores the % of renewable energy used in each country. My task is to convert the column values in 'HighRenew' column into boolean datatype. If the value for a particular country is

问题 I'm trying to work with linear functions for data conversion (like meters to feet). I'm trying to find a way to build a lambda function that returns the inverse function and another lambda function that return the composition of those functions inches_to_meters=lambda x:x*0.0254 inches_to_feets=lambda x:x*(1/12) miles_to_feets=lambda x:x*5280 composition=lambda x,y,z: lambda x,y: x(y(z)) opposite=lambda x: 1/x meters_to_inches=opposite(inches_to_meters) miles_to_inches = composition(feets_to

问题 I'm trying to work with linear functions for data conversion (like meters to feet). I'm trying to find a way to build a lambda function that returns the inverse function and another lambda function that return the composition of those functions inches_to_meters=lambda x:x*0.0254 inches_to_feets=lambda x:x*(1/12) miles_to_feets=lambda x:x*5280 composition=lambda x,y,z: lambda x,y: x(y(z)) opposite=lambda x: 1/x meters_to_inches=opposite(inches_to_meters) miles_to_inches = composition(feets_to

问题 I am a little confused on "how to do this properly": // return true: if present and number of lines != 0 boolean isValid(Optional<File> optFile) { return optFile.ifPresentOrElse(f -> return !isZeroLine(f), return false); } private boolean isZeroLine(File f) { return MyFileUtils.getNbLinesByFile(f) == 0; } I know the syntax is not correct and not compiling, but it's just for you to get the idea. How can I turn this into 'clean code'? i.e. avoid doing: if (optFile.isPresent()) {//} else {//}

问题 I am a little confused on "how to do this properly": // return true: if present and number of lines != 0 boolean isValid(Optional<File> optFile) { return optFile.ifPresentOrElse(f -> return !isZeroLine(f), return false); } private boolean isZeroLine(File f) { return MyFileUtils.getNbLinesByFile(f) == 0; } I know the syntax is not correct and not compiling, but it's just for you to get the idea. How can I turn this into 'clean code'? i.e. avoid doing: if (optFile.isPresent()) {//} else {//}

问题 I have a repository class which has a GetAsQueryable method defined as follows: public class Repository<TEntity> : IDisposable, IRepository<TEntity> where TEntity : class { internal DbSet<TEntity> _DbSet; public virtual IQueryable<TEntity> GetAsQueryable( Expression<Func<TEntity, bool>> filter = null, Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null, string includeProperties = "") { IQueryable<TEntity> query = _DbSet; if (filter != null) { query = query.Where(filter); }