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<!DOCTYPE html>
<html lang="en">
<head>
<title>Java and Scala Comparison Cheat Sheet</title>
<meta charset="utf-8">
<link rel="stylesheet" href="prism.css" data-noprefix />
<script src="prism.js"></script>
</head>
<body>
<h1>Java and Scala Comparison Cheat Sheet</h1>
<h2>Introduction</h2>
This is a reference to help people fluent in Java or Scala to become fluent in the other. I was inspired by the <a href="http://aspalliance.com/625">C# and VB.NET Comparison Cheat Sheet</a>.
<h2>Other Cheat Sheets</h2>
<a href="https://www.rea-group.com/blog/java-to-scala-cheatsheet/">https://www.rea-group.com/blog/java-to-scala-cheatsheet/</a><br>
<a href="http://www.cis.upenn.edu/~matuszek/Concise%20Guides/Concise%20Java%20to%20Scala.html">http://www.cis.upenn.edu/~matuszek/Concise Guides/Concise Java to Scala.html</a>
<h2>Source</h2>
<a href="https://github.com/shawjef3/JavaScalaCheatSheet/">https://github.com/shawjef3/JavaScalaCheatSheet/</a>
<h2>Cheat Sheet</h2>
<h3 style="text-align: center;">packages</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">package me.jeffshaw;</code></pre></td><td><pre><code class="language-scala">package me.jeffshaw</code></pre></td></tr>
<tr><td><pre><code class="language-java">import me.jeffshaw.Class;</code></pre></td><td><pre><code class="language-scala">import me.jeffshaw.Class</code></pre></td></tr>
<tr><td><pre><code class="language-java">import me.jeffshaw.Class0;
import me.jeffshaw.Class1;</code></pre></td><td><pre><code class="language-scala">import me.jeffshaw.Class0
import me.jeffshaw.Class1</code></pre>
or
<pre><code class="language-scala">import me.jeffshaw.{Class0, Class1}</code></pre></td></tr>
<tr><td><pre><code class="language-java">import me.jeffshaw.*;</code></pre></td><td><pre><code class="language-scala">import me.jeffshaw._</code></pre></td></tr>
<tr><td>☹</td><td><pre><code class="language-scala">import me.jeffshaw.{Class => RenamedClass}</code></pre></td></tr>
</table>
<h3 style="text-align: center;">classes</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">class C {}</code></pre></td><td><pre><code class="language-scala">class C</code></pre></td></tr>
<tr><td><pre><code class="language-java">class C {
public int i;
}</code></pre></td><td><pre><code class="language-scala">class C {
var i: Int = _
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">class C {
public int i = 0;
}</code></pre></td><td><pre><code class="language-scala">class C {
var i = 0
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">class C {
public int i;
public C(int i) {
this.i = i;
}
}</code></pre></td><td><pre><code class="language-scala">class C(var i: Int)</code></pre></td></tr>
<tr><td><pre><code class="language-java">class C {
public int i;
public C(int i) {
this.i = i;
}
public C() {
this(0);
}
}</code></pre></td><td><pre><code class="language-scala">class C(var i: Int) {
def this() {
this(0)
}
}</code></pre></td></tr>
</table>
<h3 style="text-align: center;">interfaces/traits</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">interface I {}</code></pre></td><td><pre><code class="language-scala">trait I</code></pre></td></tr>
<tr><td><pre><code class="language-java">interface I {
void method(int i);
}</code></pre></td><td><pre><code class="language-scala">trait I {
def method(i: Int): Unit
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">interface I {
default void method(int i) {}
}</code></pre></td><td><pre><code class="language-scala">trait I {
def method(i: Int): Unit = {}
}</code></pre></td></tr>
<tr><td>☹</td><td><pre><code class="language-scala">trait I {
val i: Int = 3
}</code></pre></td></tr>
</table>
<h3 style="text-align: center;">class and interface generics</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">class C<A> {}</code></pre></td><td><pre><code class="language-scala">class C[A]</code></pre></td></tr>
<tr><td><pre><code class="language-java">class C<A extends Comparable> {}</code></pre></td><td><pre><code class="language-scala">class C[A <: Comparable]</code></pre></td></tr>
<tr><td><pre><code class="language-java">class C<A extends Comparable & Serializable> {}</code></pre></td><td><pre><code class="language-scala">class C[A <: Comparable with Serializable]</code></pre></td></tr>
<tr><td>☹</td><td><pre><code class="language-scala">class C[A >: Nothing]</code></pre></td></tr>
<tr><td>☹</td><td><pre><code class="language-scala">class C[-A]</code></pre></td></tr>
<tr><td>☹</td><td><pre><code class="language-scala">class C[+A]</code></pre></td></tr>
</table>
<h3 style="text-align: center;">methods</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">void f(int i) {}</code></pre></td><td><pre><code class="language-scala">def f(i: Int): Unit = {}</code></pre>
or
<pre><code class="language-scala">def f(i: Int): Unit = ()</code></pre></td></tr>
<tr><td><pre><code class="language-java">int f(int i) {return i;}
f(1);</code></pre></td><td><pre><code class="language-scala">def f(i: Int): Int = i
f(1)</code></pre></td></tr>
<tr><td><pre><code class="language-java">int f(int ... ints) {return Arrays.stream(ints).sum();}
f(1, 2, 3);
f(new int[] {1, 2, 3})</code></pre></td><td><pre><code class="language-scala">def f(ints: Int*): Int = ints.sum
f(1, 2, 3)
f(Seq(1, 2, 3): _*)</code></pre></td></tr>
<tr><td><pre><code class="language-java">int[] ints;
f(ints);</code></pre></td><td><pre><code class="language-scala">val ints: Array[Int]
f(ints: _*)</code></pre></td></tr>
<tr><td><pre><code class="language-java"><T, U> U f(T arg);</code></pre></td><td><pre><code class="language-scala">def f[T, U](arg: T): U</code></pre></td></tr>
<tr><td><pre><code class="language-java">void f(List<?> args);</code></pre></td><td><pre><code class="language-scala">def f(args: List[_]): Unit</code></pre></td></tr>
<tr><td><pre><code class="language-java"><A> void f(List<? extends A> args);</code></pre></td><td><pre><code class="language-scala">def f[A](args: List[_ <: A]): Unit</code></pre></td></tr>
<tr><td><pre><code class="language-java"><A> void f(List<? super A> args);</code></pre></td><td><pre><code class="language-scala">def f[A](args: List[_ >: A]): Unit</code></pre></td></tr>
<tr><td>☹</td><td><pre><code class="language-scala">def f(arg0: Int, arg1: Int): Unit
f(arg0 = 3, arg1 = 4)
f(arg1 = 4, arg0 = 3)</code></pre></td></tr>
<tr><td><pre><code class="language-java">int f(int a){
return f(a, 0);
}
int f(int a, int b) {
return a + b
}</code></pre></td><td><pre><code class="language-scala">def f(a: Int, b: Int = 0): Int = a + b</code></pre></td></tr>
</table>
<h3 style="text-align: center;">statics</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">class C {
static int i = 0;
}</code></pre></td><td><pre><code class="language-scala">object C {
var i = 0
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">class C {
static int f(int i) {
return i + 1;
}
}</code></pre></td><td><pre><code class="language-scala">object C {
def f(i: Int): Int = i + 1
}</code></pre></td></tr>
</table>
<h3 style="text-align: center;">member access permissions</h3>
<h4 style="text-align: center;">private</h4>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">private int i;</code></pre></td><td><pre><code class="language-scala">private var i: Int</code></pre></td></tr>
</table>
<h4 style="text-align: center;">package private</h4>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">int i;</code></pre></td><td><pre><code class="language-scala">package a
class C {
private[a] var i: Int
}</code></pre></td></tr>
</table>
<h4 style="text-align: center;">instance private</h4>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td>☹</td><td><pre><code class="language-scala">private[this] var i: Int</code></pre></td></tr>
</table>
<h4 style="text-align: center;">protected</h4>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">protected int i;</code></pre></td><td><pre><code class="language-scala">protected var i: Int</code></pre></td></tr>
</table>
<h4 style="text-align: center;">public</h4>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">public int i;</code></pre></td><td><pre><code class="language-scala">var i: Int</code></pre></td></tr>
</table>
<h3 style="text-align: center;">mutability</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">int i;</code></pre></td><td><pre><code class="language-scala">var i: Int</code></pre></td></tr>
<tr><td><pre><code class="language-java">final int i;</code></pre></td><td><pre><code class="language-scala">val i: Int</code></pre></td></tr>
<tr><td><pre><code class="language-java">void f(int i) {
i = 4;
}</code></pre></td><td>☹</td></tr>
<tr><td><pre><code class="language-java">void f(final int i) {}</code></pre></td><td><pre><code class="language-scala">def f(i: Int): Unit = ()</code></pre></td></tr>
</table>
<h3 style="text-align: center;">immutable data structure</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">public class C implements Serializable {
private final int c;
public C(int c) {
this.c = c;
}
public int getC() {
return c;
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
C c1 = (C) o;
return getC() == c1.getC();
}
@Override
public int hashCode() {
return Objects.hash(getC());
}
}
</code></pre></td><td><pre><code class="language-scala">case class C(c: Int)</code></pre></td></tr>
</table>
<h3 style="text-align: center;">bean / mutable data structure</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">public class C implements Serializable {
private int c;
public C() {}
public int getC() {
return c;
}
public void setC(int c) {
this.c = c;
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
C c1 = (C) o;
return getC() == c1.getC();
}
@Override
public int hashCode() {
return Objects.hash(getC());
}
}</code></pre></td><td><pre><code class="language-scala">case class C(
@BeanProperty var c: Int
) {
def this() {
this(0)
}
}</code></pre></td></tr>
</table>
<h3 style="text-align: center;">control structures</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">return;</code></pre></td><td><pre><code class="language-scala">return</code></pre></td></tr>
<tr><td><pre><code class="language-java">return 0;</code></pre></td><td><pre><code class="language-scala">0</code></pre></td></tr>
<tr><td><pre><code class="language-java">return test ? 0 : 1;</code></pre></td><td><pre><code class="language-scala">if (test) 0 else 1</code></pre></td></tr>
<tr><td><pre><code class="language-java">if (test) {
doSomething();
} else {
doSomethingElse();
}</code></pre></td><td><pre><code class="language-scala">if (test) {
doSomething()
} else {
doSomethingElse()
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">int i = 0;
while (i < 10) {
i++;
}</code></pre></td><td><pre><code class="language-scala">var i = 0
while (i < 10) {
i += 1
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">int i = 0;
do {
i++;
} while (i < 10)</code></pre></td><td><pre><code class="language-scala">var i = 0
do {
i += 1
} while (i < 10)</code></pre></td></tr>
<tr><td><pre><code class="language-java">for (int i: collection) {}</code></pre></td><td><pre><code class="language-scala">for (i <- collection) {}</code></pre></td></tr>
<tr><td><pre><code class="language-java">for (int i: collection) {
for (int j: otherCollection) {}
}</code></pre></td><td><pre><code class="language-scala">for {
i <- collection
j <- otherCollection
} {}</code></pre></td></tr>
<tr><td><pre><code class="language-java">switch (value) {
case 0:
break;
default:
}</code></pre></td><td><pre><code class="language-scala">value match {
case 0 =>
case _ =>
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">switch (value) {
case 0:
case 1:
break;
default:
}</code></pre></td><td><pre><code class="language-scala">value match {
case 0 | 1 =>
case _ =>
}</code></pre></td></tr>
</table>
<h3 style="text-align: center;">exceptions</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">throw new Exception();</code></pre></td><td><pre><code class="language-scala">throw new Exception()</code></pre></td></tr>
<tr><td><pre><code class="language-java">try {
} catch (IOException e) {
} catch (RuntimeException e) {
} finally {}</code></pre></td><td><pre><code class="language-scala">try {
} catch {
case e: IOException =>
case e: RuntimeException =>
} finally {}</code></pre></td></tr>
</table>
<h3 style="text-align: center;">try-with-resources</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">try (InputStream i0 = new InputStream();
InputStream i1 = new InputStream()) {
}</code></pre></td><td>☹</td></tr>
</table>
<h3 style="text-align: center;">data types</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">void</code></pre></td><td><pre><code class="language-scala">Unit</code></pre></td></tr>
<tr><td><pre><code class="language-java">bool</code></pre></td><td><pre><code class="language-scala">Boolean</code></pre></td></tr>
<tr><td><pre><code class="language-java">byte</code></pre></td><td><pre><code class="language-scala">Byte</code></pre></td></tr>
<tr><td><pre><code class="language-java">char</code></pre></td><td><pre><code class="language-scala">Char</code></pre></td></tr>
<tr><td><pre><code class="language-java">int</code></pre></td><td><pre><code class="language-scala">Int</code></pre></td></tr>
<tr><td><pre><code class="language-java">long</code></pre></td><td><pre><code class="language-scala">Long</code></pre></td></tr>
<tr><td><pre><code class="language-java">float</code></pre></td><td><pre><code class="language-scala">Float</code></pre></td></tr>
<tr><td><pre><code class="language-java">double</code></pre></td><td><pre><code class="language-scala">Double</code></pre></td></tr>
<tr><td><pre><code class="language-java">Object</code></pre></td><td><pre><code class="language-scala">AnyRef</code></pre></td></tr>
<tr><td>☹</td><td><pre><code class="language-scala">Any</code></pre></td></tr>
<tr><td>☹</td><td><pre><code class="language-scala">AnyVal</code></pre></td></tr>
</table>
<h3 style="text-align: center;">null</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">null</code></pre></td><td><pre><code class="language-scala">null</code></pre></td></tr>
</table>
<h3 style="text-align: center;">equality operations</h3>
<h4 style="text-align: center;">for primitives</h4>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">==, !=</code></pre></td><td><pre><code class="language-scala">==, !=</code></pre></td></tr>
</table>
<h4 style="text-align: center;">for references</h4>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">==, !=</code></pre></td><td><pre><code class="language-scala">eq, ne</code></pre></td></tr>
<tr><td><pre><code class="language-java">.equals</code></pre></td><td><pre><code class="language-scala">==, !=</code></pre></td></tr>
</table>
<h3 style="text-align: center;">other operations</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">&&, ||, !</code></pre></td><td><pre><code class="language-scala">&&, ||, !</code></pre></td></tr>
<tr><td><pre><code class="language-java"><, >, <=, >=</code></pre></td><td><pre><code class="language-scala"><, >, <=, >=</code></pre></td></tr>
<tr><td><pre><code class="language-java">+, -, *, /, %</code></pre></td><td><pre><code class="language-scala">+, -, *, /, %</code></pre></td></tr>
<tr><td><pre><code class="language-java">&, |, ^, ~, <<, >>, >>></code></pre></td><td><pre><code class="language-scala">&, |, ^, ~, <<, >> >>></code></pre></td></tr>
<tr><td><pre><code class="language-java">+=, -=, *=, /=, %=, <<=, >>=, &=, ^=, |=</code></pre></td><td><pre><code class="language-scala">+=, -=, *=, /=, %=, <<=, >>=, &=, ^=, |=</code></pre></td></tr>
<tr><td><pre><code class="language-java">++, --</code></pre></td><td>☹</td></tr>
<tr><td><pre><code class="language-java">int i = test ? 0 : 1;</code></pre></td><td><pre><code class="language-scala">var i = if (test) 0 else 1</code></pre></td></tr>
</table>
<h3 style="text-align: center;">io</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td colspan="2">writing to files or standard error is the same</td></tr>
<tr><td><pre><code class="language-java">System.out.println("hi");</code></pre></td><td><pre><code class="language-scala">println("hi")</code></pre></td></tr>
<tr><td><pre><code class="language-java">InputStreamReader reader =
new InputStreamReader(System.in);
new BufferedReader(reader).readLine();</code></pre></td><td><pre><code class="language-scala">io.StdIn.readLine()</code></pre></td></tr>
<tr><td><pre><code class="language-java">Path path = Paths.get("file");
BufferedReader reader = Files.newBufferedReader(path);
for (String line: reader.lines().iterator()) {}</code></pre></td><td><pre><code class="language-scala">import scala.collection.JavaConverters._
val path = Paths.get("file")
val reader = Files.newBufferedReader(path)
for (line <- reader.lines.iterator.asScala) {}</code></pre>
or
<pre><code class="language-scala">val source = io.Source.fromFile("file")
for (line <- source.getLines()) {}</code></pre></td></tr>
</table>
<h3 style="text-align: center;">singleton</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">public class S {
private static S ourInstance = new S();
public static S getInstance() {
return ourInstance;
}
private S() {
}
}</code></pre></td><td><pre><code class="language-scala">class S
object Instance extends S</code></pre>
Values inside of objects are also singletons.<br>
<pre><code class="language-scala">class S
object S {
val instance = new S
}</code></pre>
Objects inside objects are also singletons<br>
<pre><code class="language-scala">class S
object S {
object Instance extends S
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">public class Number {
private int i;
private static Number ourZero = new Number(0);
public static Number getZero() {
return ourZero;
}
public Number(int i) {
this.i = i;
}
}
</code></pre></td><td><pre><code class="language-scala">class Number(val i: Int)
object Zero extends Number(0)</code></pre></td></tr>
</table>
<h3 style="text-align: center;"><code>for</code> syntax</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td>
Classic Java
<pre><code class="language-java">static List<Integer> duplicate(int i) {
return Arrays.asList(i, i);
}
List<Integer> is = Arrays.asList(1,2,3);
List<Integer> js = Arrays.asList(4,5,6);
List<Integer> duplicateSums = new ArrayList<>();
for (int i: is) {
if (i < 3) {
for (int j : js) {
for (int duplicated : duplicate(i + j)) {
duplicateSums.add(duplicated);
}
}
}
}
return duplicateSums;
</code></pre>
Java Streams
<pre><code class="language-java">static IntStream duplicate(int i) {
return IntStream.of(i, i);
}
IntStream is = IntStream.of(1,2,3);
IntStream js = IntStream.of(4,5,6);
IntStream duplicateSums =
is.filter(i -> i < 3).
flatMap(i ->
js.flatMap(j ->
duplicate(i + j)
)
);
return duplicateSums.boxed().collect(Collectors.toList());</code></pre>
</td><td><pre><code class="language-scala">def duplicate(i: Int): Seq[Int] = Seq(i, i)
val is = Seq(1,2,3)
val js = Seq(4,5,6)
for {
i <- is
if i < 3
j <- js
duplicated <- duplicate(i + j)
} yield duplicated
</code></pre></td></tr>
<tr><td><pre><code class="language-java">CompletableFuture<Integer> future0;
CompletableFuture<Integer> future1;
// Add the results of two futures.
return future0.thenCompose(value0 ->
future1.thenApply(value1 -> value0 + value1)
);</code></pre></td><td><pre><code class="language-scala">val future0: Future[Int]
val future1: Future[Int]
// Add the results of two futures.
for {
value0 <- future0
value1 <- future1
} yield value0 + value1</code></pre></td></tr>
</table>
<h3 style="text-align: center;">collections</h3><p>
<a href="https://docs.scala-lang.org/overviews/collections/conversions-between-java-and-scala-collections.html"><div style="text-align: center;">converting collections</div></a>
<h4 style="text-align: center;">arrays</h4>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">int[] ints;
int thirdInt = int[2];</code></pre></td><td><pre><code class="language-scala">var ints: Array[Int]
var thirdInt = ints(2)</code></pre></td></tr>
<tr><td><pre><code class="language-java">int[] ints = new int[] {1,2,3};</code></pre></td><td><pre><code class="language-scala">var ints = Array(1,2,3)</code></pre></td></tr>
<tr><td><pre><code class="language-java">int[][] ints = new int[][] {
{1,2,3},
{4,5,6},
{7,8,9}
};</code></pre></td><td><pre><code class="language-scala">var ints = Array(
Array(1,2,3),
Array(4,5,6),
Array(7,8,9)
)</code></pre></td></tr>
<tr><td><pre><code class="language-java">int[] ints = new int[3];</code></pre></td><td><pre><code class="language-scala">var ints = Array.ofDim[Int](3)</code></pre></td></tr>
<tr><td><pre><code class="language-java">int[][] ints = new int[3];
for (int i=0; i<3; i++) {
ints[i] = new int[3];
}</code></pre></td><td><pre><code class="language-scala">var ints = Array.ofDim[Int](3, 3)</code></pre></td></tr>
<tr><td><pre><code class="language-java">int[] ints = new int[3];
Arrays.fill(ints, 0);</code></pre></td><td><pre><code class="language-scala">var ints = Array.fill(3)(0)</code></pre></td></tr>
<tr><td><pre><code class="language-java">String[] intStrings = new String[3];
for (int i=0; i<3; i++) {
intStrings[i] = Integer.toString(i);
}</code></pre>
or
<pre><code class="language-java">IntStream.range(0, 3)
.mapToObj(Integer::toString)
.toArray();</code></pre>
</td><td><pre><code class="language-scala">var intStrings = Array.tabulate(3)(_.toString)</code></pre></td></tr>
<tr><td>☹</td><td><pre><code class="language-scala">def triple[T: ClassTag](): Array[T] = {
Array.ofDim[T](3)
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">Arrays.hashCode(array)</code></pre></td><td><pre><code class="language-scala">array.hashCode</code></pre></td></tr>
<tr><td><pre><code class="language-java">Arrays.equals(array0, array1)</code></pre></td><td><pre><code class="language-scala">array0 == array1</code></pre></td></tr>
</table>
<h4 style="text-align: center;">mutable collections</h4><p>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">List<Integer> integers = new ArrayList<>();</code></pre></td><td><pre><code class="language-scala">var integers: collection.mutable.ListBuffer[Int] =
collection.mutable.ListBuffer()</code></pre></td></tr>
<tr><td><pre><code class="language-java">List<Integer> integers = Arrays.asList(0, 1, 2);</code></pre></td><td><pre><code class="language-scala">var integers: collection.mutable.ListBuffer[Int] =
collection.mutable.ListBuffer(0, 1, 2)</code></pre></td></tr>
<tr><td><pre><code class="language-java">List<Integer> integers =
IntStream.range(0, 2).boxed().collect(Collectors.toList());</code></pre></td><td><pre><code class="language-scala">var integers: collection.mutable.ListBuffer[Int] =
collection.mutable.ListBuffer(0 to 2: _*)</code></pre></td></tr>
<tr><td><pre><code class="language-java">Set<Integer> integers = new HashSet<>();
integers.add(0);
integers.add(1);
integers.add(2);</code></pre></td><td><pre><code class="language-scala">var integers: collection.mutable.Set[Int] =
collection.mutable.Set(0, 1, 2)</code></pre></td></tr>
<tr><td><pre><code class="language-java">IntStream.range(0, 3).boxed().collect(Collectors.toSet());</code></pre></td><td><pre><code class="language-scala">var integers: collection.mutable.Set[Int] =
collection.mutable.Set(0 until 3: _*)</code></pre></td></tr>
</table>
<h4 style="text-align: center;">immutable collections</h4><p>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">List<Integer> integers = Collections.emptyList();</code></pre></td><td><pre><code class="language-scala">var integers: List[Int] = List()</code></pre></td></tr>
<tr><td><pre><code class="language-java">List<Integer> integers = Collections.unmodifiableList(
Arrays.asList(0, 1, 2)
);</code></pre></td><td><pre><code class="language-scala">var integers: List[Int] = List(0, 1, 2)</code></pre></td></tr>
<tr><td><pre><code class="language-java">List<Integer> integers =
Collections.unmodifiableList(
IntStream.range(0, 3).boxed().collect(Collectors.toList())
);</code></pre></td><td><pre><code class="language-scala">var integers: List[Int] = 0 until 3 toList</code></pre></td></tr>
<tr><td><pre><code class="language-java">Set<Integer> mutableIntegers = new HashSet<>();
mutableIntegers.add(0);
mutableIntegers.add(1);
mutableIntegers.add(2);
Set<Integer> integers =
Collections.unmodifiableSet(mutableIntegers);</code></pre></td><td><pre><code class="language-scala">var integers: Set[Int] = Set(0, 1, 2)</code></pre></td></tr>
<tr><td><pre><code class="language-java">Set<Integer> integers =
Collections.unmodifiableSet(
IntStream.range(0, 3).boxed().collect(Collectors.toSet())
);</code></pre></td><td><pre><code class="language-scala">var integers: Set[Int] = 0 until 3 toSet</code></pre></td></tr>
</table>
<h3 style="text-align: center;">lambda creation</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">Function<Integer, String> toString =
i -> i.toString();</code></pre></td><td><pre><code class="language-scala">val toString: Integer => String =
i => i.toString</code></pre></td></tr>
<tr><td><pre><code class="language-java">Function<Integer, String> toString;
String result = toString.apply(3);</code></pre></td><td><pre><code class="language-scala">val toString: Integer => String
val result = toString(3)</code></pre></td></tr>
<tr><td><pre><code class="language-java">Function<Integer, String> toString =
Object::toString;</code></pre></td><td><pre><code class="language-scala">val toString: Int => String =
_.toString</code></pre></td></tr>
<tr><td><pre><code class="language-java">IntFunction<String> toString =
Integer::toString;</code></pre></td><td><pre><code class="language-scala">val toString: Int => String =
i => i.toString</code></pre></td></tr>
<tr><td><pre><code class="language-java">Consumer<String> print =
System.out::println;</code></pre></td><td><pre><code class="language-scala">val print: String => Unit =
println</code></pre></td></tr>
<tr><td><pre><code class="language-java">IntConsumer print =
System.out::println;</code></pre></td><td><pre><code class="language-scala">val print: Int => Unit =
println</code></pre></td></tr>
<tr><td><pre><code class="language-java">Supplier<Integer> read =
() -> 3;</code></pre></td><td><pre><code class="language-scala">val read: Unit => Integer =
() => 3</code></pre></td></tr>
<tr><td><pre><code class="language-java">IntSupplier read =
() -> 3;</code></pre></td><td><pre><code class="language-scala">val read: Unit => Int =
() => 3</code></pre></td></tr>
</table>
<h3 style="text-align: center;">lambda calls</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">Function<Integer, String> toString;
toString.apply(3);</code></pre></td><td><pre><code class="language-scala">val toString: Integer => String
toString(3)</code></pre></td></tr>
<tr><td><pre><code class="language-java">Consumer<String> print;
print.accept("hi");</code></pre></td><td><pre><code class="language-scala">val print: String => Unit
print("hi")</code></pre></td></tr>
<tr><td><pre><code class="language-java">Supplier<Integer> read;
read.get();</code></pre></td><td><pre><code class="language-scala">val read: Unit => Integer
read()</code></pre></td></tr>
</table>
<h3 style="text-align: center;">comments</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">// comment</code></pre></td><td><pre><code class="language-scala">// comment</code></pre></td></tr>
<tr><td><pre><code class="language-java">/*
multiline comment
*/</code></pre></td><td><pre><code class="language-scala">/*
multiline comment
*/</code></pre></td></tr>
</table>
<h3 style="text-align: center;">lexical scoping</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td>☹</td><td><pre><code class="language-scala">val i = 0
{
val i = 1
}</code></pre></td></tr>
<tr><td><pre><code class="language-java">// cases share scope
switch (value) {
case 0: {
int i = 0;
break;
}
default: {
int i = 0;
}
}</code></pre></td><td><pre><code class="language-scala">// cases each have their own scope
value match {
case 0 =>
val i = 0;
case _ =>
val i = 0;
}</code></pre></td></tr>
</table>
<h3 style="text-align: center;">statement sequencing</h3>
<table style="margin-left:auto; margin-right:auto;">
<tr><th>Java</th><th>Scala</th></tr>
<tr><td><pre><code class="language-java">int i = 0; int j = 1;</code></pre></td><td><pre><code class="language-scala">var i = 0; var j = 1</code></pre>
or
<pre><code class="language-scala">var i = 0
var j = 1</code></pre></td></tr>
</table>
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<table style="margin-left:auto; margin-right:auto;">
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