Hello World

A sample go program is show here.

package main

import "fmt"

func main() {
  message := greetMe("world")
  fmt.Println(message)
}

func greetMe(name string) string {
  return "Hello, " + name + "!"
}

Run the program as below:

$ go run hello.go
Variables

Normal Declaration:

var msg string
msg = "Hello"

Shortcut:

msg := "Hello"
Constants
const Phi = 1.618
Strings
str := "Hello"

Multiline string

str := `Multiline
string`
Numbers

Typical types

num := 3          // int
num := 3.         // float64
num := 3 + 4i     // complex128
num := byte('a')  // byte (alias for uint8)

Other Types

var u uint = 7        // uint (unsigned)
var p float32 = 22.7  // 32-bit float
Arrays
// var numbers [5]int
numbers := [...]int{0, 0, 0, 0, 0}
Pointers
func main () {
  b := *getPointer()
  fmt.Println("Value is", b)
func getPointer () (myPointer *int) {
  a := 234
  return &a
a := new(int)
*a = 234

Pointers point to a memory location of a variable. Go is fully garbage-collected.

Type Conversion
i := 2
f := float64(i)
u := uint(i)
Slice
slice := []int{2, 3, 4}
slice := []byte("Hello")
Condition
if day == "sunday" || day == "saturday" {
  rest()
} else if day == "monday" && isTired() {
  groan()
} else {
  work()
}
if _, err := doThing(); err != nil {
  fmt.Println("Uh oh")
Switch
switch day {
  case "sunday":
    // cases don't "fall through" by default!
    fallthrough

  case "saturday":
    rest()

  default:
    work()
}
Loop
for count := 0; count <= 10; count++ {
  fmt.Println("My counter is at", count)
}
entry := []string{"Jack","John","Jones"}
for i, val := range entry {
  fmt.Printf("At position %d, the character %s is present\n", i, val)
n := 0
x := 42
for n != x {
  n := guess()
}
Scanner
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
long ln = sc.nextLong();
double dn = sc.nextDouble();
String s = sc.read(); //sc.readLine();
BufferedReader
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int n = Integer.parseInt(br.readLine());
int a[] = new int[n];
//n elements in one line
StringTokenizer st = new StringTokenizer(br.readLine());
for(int i = 0; i < n; ++i){
  a[i] = Integer.parseInt(st.nextToken());
}
StreamTokenizer
private static StreamTokenizer st;
private static int nextInt() throws IOException{
  st.nextToken();
  return (int)st.nval;
}
private static long nextLong() throws IOException{
  st.nextToken();
  return (long)st.nval;
}
private static double nextDouble() throws IOException{
  st.nextToken();
  return st.nval;
}
private static String read() throws IOException{ //don't recommend to read string with this i/o
  st.nextToken();
  return st.sval;
}
public static void main(String[] args){
  st = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
  int n = nextInt();
  long ln = nextLong();
  double dn = nextDouble();
  String s = read();
}
PrintWriter
PrintWriter pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
pw.println("Hello world!");
pw.close();
Condition
if day == "sunday" || day == "saturday" {
  rest()
} else if day == "monday" && isTired() {
  groan()
} else {
  work()
}
if _, err := doThing(); err != nil {
  fmt.Println("Uh oh")
Variable
NAME="John"
echo $NAME
echo "$NAME"
echo "${NAME}
Condition
if [[ -z "$string" ]]; then
  echo "String is empty"
elif [[ -n "$string" ]]; then
  echo "String is not empty"
fi