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