Q: How to build an entity in java stream? There is entity :
@SuperBuilder
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Student {

    private String name;

    private Integer age;

I make my way down the stream and collect a list of my students with the help of a builder
public List<Student> getStudent(Inputstream students) {
 return new BufferedReader(new InputStreamReader(students)).lines()
        .map(String::trim)
        .filter(line -> line.startsWith("a"))
        .map(line ->
            Student.builder()
                .name(line.substring(0, line.indexOf("this name")))
                .age(line.substring(line.indexOf("name")))
                .build())
        .collect(Collectors.toList());

}

Would this use of the builder be correct?

A: Yes, this usage is correct. You don't break any of the rules and patterns familiar to me. Besides, you can do some refactors like that:
public List<Student> getStudent(Inputstream students) {
 return new BufferedReader(new InputStreamReader(students)).lines()
        .map(String::trim)
        .filter(line -> line.startsWith("a"))
        .map(this::makeStudent)
        .collect(toList());

}

private Student makeStudent(final String source){
    return Student.builder()
                  .name(source.substring(0, source.indexOf("this name")))
                  .age(source.substring(source.indexOf("name")))
                  .build();
}

