Go Java, Go!

GO
JAVA,
GO!
ANDRES ALMIRAY IXCHEL RUIZ
@AALMIRAY @IXCHELRUIZ
ANDRESALMIRAY.COM IXCHELRUIZ.COM

@ixchelruiz @aalmiray
GO: GETTING STARTED
Official (executable) documentation
https://gobyexample.com/
Test your knowledge with
https://github.com/cdarwin/go-koans

HELLO WORLD (JAVA)
package main;
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World");
}
}
$ java main/HelloWorld.java
$ javac –d classes main/HelloWorld.java
$ java –cp classes main.HelloWorld

HELLO WORLD (GO)
package main
import "fmt"
func main() {
fmt.Println("Hello World")
}
$ go run hello-world.go
$ go build hello-world.go
$ ./hello-world

VALUES (JAVA)
package main;
public class Values {
System.out.println("go" + "lang");
System.out.println("1+1 = "+ (1+1));
System.out.println("7.0/3.0 = " + (7.0/3.0));
System.out.println(true && false);
System.out.println(true || false);
System.out.println(!true);
}
}

VALUES (GO)
package main
import "fmt"
func main() {
fmt.Println("go" + "lang")
fmt.Println("1+1 = ", 1+1)
fmt.Println("7.0/3.0 = ", 7.0/3.0)
fmt.Println(true && false)
fmt.Println(true || false)
fmt.Println(!true)
}

VALUES (OUTPUT)
golang
1+1 = 2
7.0/3.0 = 2.3333333333333335
false
true
false

CONDITIONS (JAVA)
package main;
public class Conditions {
if (7%2 == 0) {
System.out.println("7 is odd");
} else {
System.out.println("7 is even");
}
}
}

CONDITIONS (GO)
package main
import "fmt"
func main() {
if 7%2 == 0 {
fmt.Println("7 is odd")
} else {
fmt.Println("7 is even")
}
}

VISIBILITY
• There are 4 visibility modifiers in Java:
• public, protected, private, and package private
• Well… technically 5 -> modules
• There is a case convention in Go
• Symbols starting with uppercase as public
• Symbols starting with lowercase are private
• That’s it, no more, move along.

TYPE INFERENCE (JAVA)
• We’ve got verbosity reduction with the <> operator (JDK 7)
List<String> strings = new ArrayList<>();
• Next we’ve got type inference for local variables (JDK 10)
var strings = new ArrayList<String>();
• Use var in lambda expression arguments (JDK 11)

TYPE INFERENCE (GO)
• You may define and assign variables in this way
var strings = []string{"a","b","c"};
• Or use the short notation
strings := []string{"a","b","c"};

COLLECTIONS
• Slices and Maps (collections)
var sliceOfStrings = []string{"a", "b", "c"}
mapOfValues := make(map([string]int))
mapOfValues["foo"] = 1
anotherMap := map[string]int{"foo": 1}

ARRAYS
• Arrays look like slices but their length is part of the type
var an_array [5]int
another_one := [5]int{1,2,3,4,5}
• Any function that takes [5]int can’t take [4]int or any other
array with a different length than 5.

FUNCTIONS
• Functions may have zero or more arguments
• Return type is defined after the argument list
• Symbol naming convention applies
func fib(n int) int {
if n <= 1 {
return n
}
return fib(n-1) + fib(n-2)
}

MULTIPLE RETURN VALUES
• Return as many values as needed
func thisAndTheOtherThing() (int,string) {
// do some work
return 0, "OK"
}

FUNCTIONS AS CODE
• Just like lambda expressions
package main
import "fmt"
func greeting_gen() func(string) string {
return func(s string) string {
return "Hello " + s
}
}
func main() {
fmt.Println(greeting_gen()("Go"))
}

THERE IS NO CLASS

BUT THERE IS STRUCT
• There’s no equivalent to POJOs in Go
• You may create new types by leveraging structs
type Person struct {
name string
age int
}

CONSTRUCTORS
package main
import "fmt"
name string
age int
}
func main() {
p1 := Person{"Duke", 23}
p2 := Person{name: "Duke", age: 23}
}

SPOT THE COMPILE ERROR
package main
import "fmt"
name string
age int
}
func main() {
}

SPOT THE COMPILE ERROR
package main
import "fmt"
name string
age int
}
func main() {
p1 := Person{"Duke", 23} // UNUSED!
}

THERE ARE NO METHODS

ATTACH FUNCTIONS TO TYPES
package main
import "fmt"
name string
age int
}
func (p *Person) printAge() {
fmt.Println("Age is = ", p.age)
}
func main() {
p1.printAge()
}

WHILE LOOP (JAVA)
package main;
public class While {
int i = 0;
while(i <= 3) {
System.out.println(i);
i++;
}
}
}

WHILE LOOP (GO)
package main
import "fmt"
func main() {
i := 0
for i <= 3 {
fmt.Println(i)
i++
}
}

FOR LOOP (JAVA)
package main;
public class For {
for(int i = 0; i <=3; i++) {
System.out.println(i);
}
}
}

FOR LOOP (GO)
package main
import "fmt"
func main() {
for i:= 0; i <= 3; i++ {
fmt.Println(i)
}
}

INFINITE LOOPS (JAVA)
package main;
public class Infinite {
while(true) {
System.out.println("Infinite loop");
break;
}
}
}

package main;
for(;;) {
break;
}
}
}

package main;
do {
break;
} while(true);
}
}

INFINITE LOOPS (GO)
package main
import "fmt"
func main() {
for {
fmt.Println("Infinite loop")
break
}
}

INTERFACES
• Interfaces are implemented automatically as long as the type
matches all methods.
• The interface{} type is roughly equivalent to
java.lang.Object

package main
import "fmt"
import "math"
type geometry interface {
area() float64
perim() float64
}
type rect struct {
width, height float64
}
type circle struct {
radius float64
}

func (r rect) area() float64 {
return r.width * r.height
}
func (r rect) perim() float64 {
return 2*r.width + 2*r.height
}
func (c circle) area() float64 {
return math.Pi * c.radius * c.radius
}
func (c circle) perim() float64 {
return 2 * math.Pi * c.radius
}

func measure(g geometry) {
fmt.Println(g)
fmt.Println(g.area())
fmt.Println(g.perim())
}
func main() {
r := rect{width: 3, height: 4}
c := circle{radius: 5}
measure(r)
measure(c)
}

ERRORS
• Go doesn’t have exceptions like Java does
• Errors are just another type that can be handled
• Use the multiple return feature to “throw” errors
func f1(arg int) (int, error) {
if arg == 42 {
return -1, errors.New("can't work with 42")
}
return arg + 3, nil
}

TYPE CLONE VS TYPE ALIAS
• Type cloning
type foo int
• Type aliasing
type bar = int
• Instances of foo behave like int BUT they are not the same
as int, that is, a method taking an int as argument can’t take
a foo.
• Instances of bar are identical to int, that is, anywhere an int
fits so does a bar and viceversa.

HELLO WORLD (JAVA)
$ time java main/HelloWorld.java
Hello World
real 0m0.538s
user 0m0.918s
sys 0m0.069s
$ javac -d classes main/HelloWorld.java
$ time java -cp classes main.HelloWorld
Hello World
real 0m0.112s
user 0m0.104s
sys 0m0.029s

HELLO WORLD (GO)
$ time go run hello-world.go
Hello World
real 0m0.191s
user 0m0.135s
sys 0m0.080s
$ go build hello-world.go
$ time ./hello-world
Hello World
real 0m0.006s
user 0m0.001s
sys 0m0.004s

TIMES
Java Go Percentage
Run
Real 0.538 0.191 65.59
User 0.918 0.135 85.29
Sys 0.069 0.080 -15.94
Compile & Run
Real 0.112 0.006 94.64
User 0.104 0.001 99.03
Sys 0.029 0.004 86.20

HTTPS://GRPC.IO
gRPC is a modern, open source, high-performance remote
procedure call (RPC) framework that can run anywhere. It
enables client and server applications to communicate
transparently, and makes it easier to build connected systems.
Stream data between client and server, in either direction, event
both directions at the same time.

HTTPS://WEBASSEMBLY.ORG/
WebAssembly (abbreviated Wasm) is a binary instruction format
for a stack-based virtual machine. Wasm is designed as a
portable target for compilation of high-level languages, enabling
deployment on the web for client and server applications.

GO + WEBASSEMBLY
https://github.com/golang/go/wiki/WebAssembly

HTTP://ANDRESALMIRAY.COM/NEWSLETTER
HTTP://ANDRESALMIRAY.COM/EDITORIAL

THANK YOU!
ANDRES ALMIRAY IXCHEL RUIZ
@AALMIRAY @IXCHELRUIZ
ANDRESALMIRAY.COM IXCHELRUIZ.COM

Go Java, Go!

More Related Content

What's hot (20)

Similar to Go Java, Go! (20)

More from Andres Almiray (20)

Recently uploaded (20)

Go Java, Go!