canpan14 :
My basic class is:
public class Student {
public String name;
public String className; // In real code I'd have a second object for return to the end user
public List<String> classes; // Can be zero
}
I'd like to flatten it out so I can return something like
[
{
"name":"joe",
"class":"science"
},
{
"name":"joe",
"class":"math"
},
]
Obviously a stupid example for the sake of simplicity.
The only way I've been able to do it is through some long winded code like:
List<Student> students = getStudents();
List<Student> outputStudents = new ArrayList<>();
students.forEach(student -> {
if(student.getClasses().size() > 0) {
student.getClasses().forEach(clazz -> {
outputStudents.add(new Student(student.getName(), clazz));
});
} else {
outputStudents.add(student);
}
});
Looking if there is a way to simplify this, maybe using flapMap?
jwismar :
Yes, you should be able to do something like this:
Student student = ?
List<Student> output =
student
.getClasses()
.stream()
.map(clazz -> new Student(student.getName, student.getClassName, clazz))
.collect(Collectors.toList());
For a single student. For a collection of students it's a little more complicated:
(Updated due to observation in comment from @nullpointer. Thanks!)
List<Student> listOfStudents = getStudents();
List<Student> outputStudents =
listOfStudents
.stream()
.flatMap(student -> {
List<String> classes = student.getClasses();
if (classes.isEmpty()) return ImmutableList.of(student).stream();
return classes.stream().map(clazz -> new Student(student.getName(), student.getClassName(), ImmutableList.of(clazz)));
})
.collect(Collectors.toList());