machince-coding-checklist

1. Writing in a file
2. Formatting string in simple java
3. Reading from a file inm java
4. forEAch Stream, interate wihtotu strem
5. intin set, and list
6. config readers
7. Enum ordinal
8. search in a set by class names

9. Sorting a list of Object

List<Account> topAccounts = new ArrayList<>(accounts.values());
topAccounts.sort((a, b) -> Double.compare(b.getBalance(), a.getBalance()));

10. Sum in a stream

int withdrawalSum = (int) trxList.stream()
                        .filter(trx -> trx.getType() == Trx.Type.WITHDRAWAL)
                        .mapToDouble(Trx::getAmount)
                        .sum();

11. Sort a hashmap in reverse Order

Map<Integer, AccountWithTrx> topAccounts = new HashMap<>();
Map<Integer, AccountWithTrx> topAccountSorted = new java.util.TreeMap<>(java.util.Collections.reverseOrder());

12. Retrun Top N entries from the map

// Return only the top N entries (up to 3) as a new map
        return topAccounts.entrySet().stream()
                .limit(N)
                .collect(java.util.LinkedHashMap::new,
                        (m, e) -> m.put(e.getKey(), e.getValue()),
                        java.util.LinkedHashMap::putAll
                );

13. Remove From Java Array

ArrayList<Integer> num = new ArrayList<>();
boolean removed = num.removeIf(n -> (n % 3 == 0));

14. Prefix matching in Java

String myStr = "Hello";
System.out.println(myStr.startsWith("Hel"));

15. Iterate a List

for (Object o: objects) {
    // Do operation on o
}

16. Iterate over a map

Map<String, String> map = ...
for (Map.Entry<String, String> entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

17. Search in List of Object

Optional<Person> result = people.stream()
    .filter(p -> p.getName().equals("Rama") && p.getAge() == 25)
    .findFirst();

if (result.isPresent()) {
    System.out.println("Found: " + result.get().getName());
} else {
    System.out.println("Not found");
}

List<Person> matches = people.stream()
    .filter(p -> p.getCity().equals("Vrindavan") && p.getAge() > 20)
    .collect(Collectors.toList());

🧠 Notes:

• Use .findFirst() or .findAny() when you just want one.
• Use .collect(Collectors.toList()) to get all matches.
• You can also combine with .map() or .sorted() if needed.