Java Hacks

List<String> array_list = new ArrayList<String>(pq1);

// \s is regular expression for space. + stands for more than one space
str.split("\\s+");

Double.compare(doubel, double2)

// 2 D array arr[][]
int rows  =  arr.length;
// Numbers of column in row 0
int colums = arr[0].length;

// Trim whitespace from 'str'
str.trim();

// Convert integer 'i' to char based on th base 'RADIX'
char ch = Character.forDigit(i, RADIX);

// Another way 
int i = 1;
char b = (char)(i + 'a');

Set<String> hSet = new HashSet<String>();

// Add values
hSet.add("Set");
hSet.add("List");

List<String> list = new ArrayList<String>(hSet);

// map.values() gives a Collection with all the values in HashMap
HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
Collection<Integer> values = map.values();
// ArrayList has a constructor that accepts a collection.
List<Integer> valuesList  = new ArrayList<Integer>(values);