Sorting Collections with Multiple Fields Using Java 8 Lambda's

The provided sorting code appears incomplete and might not produce the expected sorted order. Let's dive into a more efficient and comprehensive approach using Java 8 lambda's.

using Java 8 lambda's

Java 8 simplifies list sorting by providing intuitive lambda expressions that allow for concise and easy-to-read code. Consider the following:

Collections.sort(reportList, Comparator.comparing(Report::getReportKey)
            .thenComparing(Report::getStudentNumber)
            .thenComparing(Report::getSchool));

This lambda-based approach sequences the comparison process, effectively sorting the list based on the specified fields in the order of precedence defined by the .thenComparing() method.

Original Code Analysis

The original code you provided concatenate the strings for the report key, student number, and school:

return (record1.getReportKey()   record1.getStudentNumber()   record1.getSchool())
        .compareTo(record2.getReportKey()   record2.getStudentNumber()   record2.getSchool());

Instead, for proper sorting, you should compare the fields independently.

Enhanced Sort Function

Here's an enhanced version of the sort function using the lambda syntax:

Collections.sort(reportList, (record1, record2) -> {
        int reportKeyComparison = record1.getReportKey().compareTo(record2.getReportKey());
        if (reportKeyComparison != 0) {
            return reportKeyComparison;
        }

        int studentNumberComparison = record1.getStudentNumber().compareTo(record2.getStudentNumber());
        if (studentNumberComparison != 0) {
            return studentNumberComparison;
        }

        return record1.getSchool().compareTo(record2.getSchool());});

This code directly compares the individual fields, providing a more accurate sort order.