System.out.print("Hello, World!"); System.out.println("Hello, World!"); 

print("Hello, World!") println("Hello, World!") 

final int x; final int y = 1; 

val x: Int val y = 1 

int w; int z = 2; z = 3; w = 1; 

var w: Int var z = 2 z = 3 w = 1 

final String name = null; String lastName; lastName = null 

val name: String? = null var lastName: String? lastName = null var firstName: String firstName = null // Compilation error!! 

if(text != null){ int length = text.length(); } 

val length = text?.length val length = text!!.length // NullPointerException if text == null 

String name = "John"; String lastName = "Smith"; String text = "My name is: " + name + " " + lastName; String otherText = "My name is: " + name.substring(2); 

val name = "John" val lastName = "Smith" val text = "My name is: $name $lastName" val otherText = "My name is: ${name.substring(2)}" 

String text = "First Line\n" + "Second Line\n" + "Third Line"; 

val text = """ |First Line |Second Line |Third Line """.trimMargin() 

String text = x > 5 ? "x > 5" : "x <= 5"; 

val text = if (x > 5) "x > 5" else "x <= 5" 

final int andResult = a & b; final int orResult = a | b; final int xorResult = a ^ b; final int rightShift = a >> 2; final int leftShift = a << 2; 

val andResult = a and b val orResult = a or b val xorResult = a xor b val rightShift = a shr 2 val leftShift = a shl 2 

if(x instanceof Integer){ } final String text = (String) other; if(x >= 0 && x <= 10 ){} 

if (x is Int) { } val text = other as String if (x in 0..10) { } 

if(a instanceof String){ final String result = ((String) a).substring(1); } 

if (a is String) { val result = a.substring(1) } 

final int x = // value; final String xResult; switch (x){ case 0: case 11: xResult = "0 or 11"; break; case 1: case 2: //... case 10: xResult = "from 1 to 10"; break; default: if(x < 12 && x > 14) { xResult = "not from 12 to 14"; break; } if(isOdd(x)) { xResult = "is odd"; break; } xResult = "otherwise"; } final int y = // value; final String yResult; if(isNegative(y)){ yResult = "is Negative"; } else if(isZero(y)){ yResult = "is Zero"; }else if(isOdd(y)){ yResult = "is Odd"; }else { yResult = "otherwise"; } 

val x = // value val xResult = when (x) { 0, 11 -> "0 or 11" in 1..10 -> "from 1 to 10" !in 12..14 -> "not from 12 to 14" else -> if (isOdd(x)) { "is odd" } else { "otherwise" } } val y = // value val yResult = when { isNegative(y) -> "is Negative" isZero(y) -> "is Zero" isOdd(y) -> "is odd" else -> "otherwise" } 

for (int i = 1; i < 11 ; i++) { } for (int i = 1; i < 11 ; i+=2) { } for (String item : collection) { } for (Map.Entry<String, String> entry: map.entrySet()) { } 

for (i in 1 until 11) { } for (i in 1..10 step 2) {} for (item in collection) {} for ((index, item) in collection.withIndex()) {} for ((key, value) in map) {} 

final List<Integer> numbers = Arrays.asList(1, 2, 3); final Map<Integer, String> map = new HashMap<Integer, String>(); map.put(1, "One"); map.put(2, "Two"); map.put(3, "Three"); // Java 9 final List<Integer> numbers = List.of(1, 2, 3); final Map<Integer, String> map = Map.of(1, "One", 2, "Two", 3, "Three"); 

val numbers = listOf(1, 2, 3) val map = mapOf(1 to "One", 2 to "Two", 3 to "Three") 

for (int number : numbers) { System.out.println(number); } for (int number : numbers) { if(number > 5) { System.out.println(number); } } 

numbers.forEach { println(it) } numbers.filter { it > 5 } .forEach { println(it) } 

final Map<String, List<Integer>> groups = new HashMap<>(); for (int number : numbers) { if((number & 1) == 0){ if(!groups.containsKey("even")){ groups.put("even", new ArrayList<>()); } groups.get("even").add(number); continue; } if(!groups.containsKey("odd")){ groups.put("odd", new ArrayList<>()); } groups.get("odd").add(number); } // or Map<String, List<Integer>> groups = items.stream().collect( Collectors.groupingBy(item -> (item & 1) == 0 ? "even" : "odd") ); 

val groups = numbers.groupBy { if (it and 1 == 0) "even" else "odd" } 

final List<Integer> evens = new ArrayList<>(); final List<Integer> odds = new ArrayList<>(); for (int number : numbers){ if ((number & 1) == 0) { evens.add(number); }else { odds.add(number); } } 

val (evens, odds) = numbers.partition { it and 1 == 0 } 

final List<User> users = getUsers(); Collections.sort(users, new Comparator<User>(){ public int compare(User user, User otherUser){ return user.lastname.compareTo(otherUser.lastname); } }); // or users.sort(Comparator.comparing(user -> user.lastname)); 

val users = getUsers() users.sortedBy { it.lastname }