char ch[] = s.toCharArray();

• Char Array to String
  Adding all char array character to a single string String.valueOf(chararr);

• Reversing a string StringBuilder s = new StringBuilder("String"); s.reverse()

• Converting Arrays to list You can only convert wrapper class to list Integer arr[] = {blah....}; list<Object> al = Arrays.asList(arr);

• Array fill
  Filling array with same number
  Array.fill(arr,-1);

• Array Equal Return boolean comparing arrays
  Arrays.equals(arr1,arr2);

• Array Sort Sorting array
  Arrays.sort(arr);

• Array BinarySearch Searching a number using binarySearch
  Arrays.binarySearch(arr,10);

• Enhanced Get Element Used in insertion of frequency
  hm.getOrDefault(arr[i],0)+1 ;
  hm.put(arr[i],hm.getOrDefault(arr[i],0)+1)
• Iterator
  HashMap<Integer,String> languages;
  for (Entry<Integer,String> entry : languages.entrySet()) {
  System.out.print(entry.getKey());
  System.out.print(entry.getValue());
  }

• MIN Heap
  PriorityQueue<Integer> pq = new PriorityQueue<>((a,b)->a-b);
• MAX Heap
  PriorityQueue<Integer> pq = new PriorityQueue<>((a,b)->b-a);

• If statement return a value
  (a>b) ? true : false ;

• String T to T
  Double.parseDouble("1.223") Integer.parseInt("123") Float.parseFloat("23.23")

• Decimal after point till x
  double d1 = 1.23232
  DecimalFormat df = new DecimalFormat()
  d1 = df.format(d1)