Table of Content:

1. String
2. Array
3. Map
4. Set
5. Stack
6. Queue

Common interface Collection has method isEmpty().

1. String

Get char at index: use .charAt(), return char.

Operations:

s.length()
s1.equals(s2)
substring(start, end)

replaceAll(regex, str);
split(regex);
indexOf(CharSequence); // which is basically a string

2. Array

normal array: int[] xxx

To get length: arr.length

Arrays.sort(arr);

for (int each: xxx) {
    // you can do this
}

// to convert to List
// Do it manually

List<E>

Collections.sort(list, comparator);
list.sort(comparator);

for (E each: list) {
    // ok, too
}

// to convert to array
// Do it manually

3. Map

Map<typeofkey, typeofvalue> xxx = new HashMap<>();

If to use primitive types like int and char, use wrapper class for the type decleration: Integer and Character.

Map operations:

.put(k, v) .putIfAbsent
.get(k); .getOrDefault
.remove(k)
.containsKey(k);
.containsValue(k)
.entrySet
.keySet
.values
.size

4. Set

Set<type> set = new HashSet<>()

Set operations

.add
.contains
.size
.remove

for (type each : set) {
    ...
}

5.Stack

Stack<type> stack = new Stack<>()

Stack operations

.peek()
.pop()
.push()
.empty()

6.Queue

Queue<T> queue = new LinkedList();
PriorityQueue(Comparator)

.offer()
.poll()
.peek()