[JAVA] Basic writing of various programming languages (self-memo)

If I was doing various programming language learning sites at super speed, I would like to summarize how to write each language. For the time being, only super basic. .. ..

What is written here is a compilation of research by the author who is a super beginner in programming.

I would be grateful if you could point out any mistakes.

List of programming languages handled here

• C
• Python3
• Java
• JavaScript
• Ruby
• C#

It is difficult to clearly describe the difference in specifications for each language, so it is for reference only.

output

hello_world.c

printf("Hello World");
printf("%d",num);  //Integer output
printf("%f",data);  //Real number output
printf("%c",mozi);  //Character output
printf("%s",str);  //String output

hello_world.py

print("Hello World")
print(num)
print(str)

#Single quote "', And double quotes ""Either is acceptable(Because it is troublesome, I said ""」)

hello_world.java

System.out.println("Hello World"); //The second character from the back of println is l(Elle)

hello_world.js

console.log("Hello World");
console.log(num);
console.log(str);

hello_world.rb

puts "Hello World"
puts "#{str}"  #「#{variable}Can replace the value with

hello_world.cs

Console.WriteLine("Hello World");  //With line breaks
Console.Write("Hello World");  //No line breaks
Console.WriteLine("{0}",num);

comment

comment.c_&_comment.java_&_comment.js_&_comment.cs

//It's a comment

comment.py_&_comment.rb

#It's a comment

Variable declaration (initialization)

box.c

int num = 0;
char mozi = 'a'; //Only one letter
char str[] = "abc";  //String

box.py_&_box.rb

num = 0  #Numerical value
str = "abc"  #String

box.java

int num = 0;  //integer
double num = 3.14;  //Real number
String str = "abc";  //String
boolean bool = true; //Boolean value

box.js

var num = 0;
var str = "abc";

box.cs

int num = 0;
string str = "abc";
bool a = true;
var x = 10;
var y = "abc";

##String concatenation

#### **`strlink.c`**
```c

include <string.h>
char str1[80] = "DRAGON";
char str2[] = "QUEST";
strcat(str1,str2);
printf("%s",str1);

Postscript: It is necessary to create extra elements of the array for the amount to be concatenated.(ex:str1[80]) Thank you for pointing out, shiracamus!

strlink.py

str1 = "DRAGON"
str2 = "QUEST"
print(str1 + str2)

strlink.java

String str1 = "DRAGON";
String str2 = "QUEST";
System.out.println(str1 + str2);

strlink.js

var str1 = "DRAGON";
var str2 = "QUEST";
console.log(str1 + str2);

strlink.rb

str1 = "DRAGON"
str2 = "QUEST"
puts str1 + str2

##Type conversion(cast)

convert.c

 itoa (num, str, 10); // Decimal // Number (int num) to string (str)
 atoi (str); // Number from string

convert.py

 str (num) # From numeric type to string type
 int (str) #string to numeric

Java has automatic type conversion and manual type conversion

convert.java

 System.out.println (month + "month" + date + "day"); // int type month variable and date variable are automatically converted to String type

cast.java

int num = 13;
 System.out.println ((double) num); // Manual type conversion Output result is "13.0"

convert.rb

 puts 1.to_s + "month" + 1.to_s + "day" #to_s to convert numbers to strings

 num = "13" # This is a string object because it is enclosed in double quotes
 Convert strings to numbers with puts num.to_i #to_i

convert.cs

int num = int.Parse(str);
string str = (string)123;

##if statement

if.c_&_if.java_&_if.js

if(num == 100 && score > 1000){
 //処理文
}
 else if(num < 100 || score != 1000){
 //処理文
}
else{
 //処理文
}

if.py

if num == 100 and score > 1000:
 #Processing statement
elif num > 100 or score != 1000:
 #Processing statement
else:
 #Processing statement

if.rb

if num == 100 && score > 1000
 #Processing statement
 elsif num > 100 || score != 1000
 #Processing statement
else
 #Processing statement
end
# (Processing statement if conditional expression) is also possible

##switch statement

switch.c_&_switch.java

switch(num){
 case 0:
 //処理文
   break;
 case 1:
 //処理文
   break;
 default:
 //処理文
   break;
}

#case statement

case.rb

case x
 when 1
 #Processing statement
 when 2
 #Processing statement
 else
 #Processing statement
end

##input

input.c

 scanf ("% d", & num); // Integer input
 scanf ("% lf", & data); // Real number input
 scanf ("% c", mozi); // Enter characters
 scanf ("% s", str); // String input

input.py

 count = input () #variable type irrelevant

input.java

 import java.util.Scanner; // call external library

class Main{
 public static void main(String[] args){
 Scanner scanner = new Scanner (System.in); // Initialize Scanner
 String name = scanner.next (); // Waiting for input from the console
 }
}

input.rb

 The input received by count = gets #gets is a string

##Array & List

array.c

int a[] = {1, 2, 3, 4};
int a[3][4];

The image is http://www.cc.kyoto-su.ac.jp/~yamada/programming/array.From html

array.java

String names[] = {"apple","banana"};

array.js

var names = ["apple","banana"];
 console.log (names.length); // Get the number of elements in the array

array.rb

names = ["apple","banana"]
 puts names.size # Get the number of elements in the array
 names.push ("grape") # Add element to end of array

list.py

lists = ["apple","banana",200,300]
 lists.append ("pizza") #Add element to end of list

##dictionary(dict) (Associative array) (hash)

dict.py_&_dict.js

 fruits = {"apple": 200, "banana": 300} // Variable = {"key": value, "key": value}

hash.rb

 fruits = {"apple" => "200", "banana" => "300"} #variable = "key" => "value"}
 puts fruits ["apple"] # Retrieving values
 fruits ["grape"] = "400" #Add data

##symbol A feature in Ruby. Although it looks like a string in the code, it is faster than a string object for comparison, search, and reference. Often used for hash keys.

symbol.rb

fruits = {:apple => "200", :banana => "300"}
puts fruits[:apple]

#each statement A method that iterates over an array or hash in order from the first data

each.rb

 fruits.each do |key,value|  #Array.each do |variable|
 puts "#{key}:#{value}"
end

##for statement

for.c_&_for.js

for(int i = 0; i < 10; i++){
 //処理文
}

for.java

for(int i = 0; i < 10; i++){
 System.out.println(i);
}

String names = {"apple","banana"};
 for (int i = 0; i <names.length; i ++) {// Count the number of elements in the array with the length method
 System.out.println("eat" + names[i]);
}

exfor.java

String names = {"apple","banana"};
 for (String name: names) {// The element itself of the array names is assigned to the variable name
 System.out.println(name);
}

for.py

for i in range(0,10):
 print(i)

for.rb

 for i in 0..9 do # (do can be omitted)
 puts i
end

##while statement

while.c_&_while.java_&_while.js

int x = 1;
while(x <= 100){
 //処理文
 x++;
}

while.py

x = 1
while x <= 100:
 #Processing statement
 x += 1

while.rb

i = 1
 while i <= 100 do #do can be omitted
 #Processing statement
 i += 1
end

##Method(function)

func.c

include <stdio.h>
int number(int num){
 printf ("The number is% d \ n", num);
  num += 1;
  return num;
}

int main()
{
  int data = number(1);
  printf("%d\n",data);
  return 0;
}

func.py

# Scope of variable name From here (range where variables can be used)
def hello(name): 
  print("hello" + name)
  name = "hello"
  return name  
# Scope so far

hi = hello("world")
print(hi)

func.java

class Main{
 public static void main(String[] args){
  String hi; 
  hi = hello("world");
  System.out.println(hi);
 }

 public static String hello(String name){
  System.out.println("Hello" + name);
  name = "hello";
  return name;
 }
}

func.js

function number(num){
  console.log(num);
  num += 1;
  return num;
}

var data = number(1);
console.log(data);

func.rb

def number(num)
 puts num
 num += 1
 return num
end

data = number(1)
puts(data)

In Ruby, each type of object has its own method(↓ is an example)

func1.rb

 puts "Hello" .length # Output the number of characters in the string object
 puts 3.14.round # Output rounded numbers
 puts "Hello" .reverse # Invert characters and output

##Library(module)(header file)

module.c

include <~.h>

module.py_&_module.java

import ~

##What I noticed / notes -It seems that the specifications are quite different between Python 2 and Python 3. -In Python you can use either single or double quotes(I think)

• Python,In Ruby, ";I don't need -C language is difficult to use when I try to touch other languages()
• C,Python,Snake case is customary for variable declaration in Ruby(int user_number;) -Camelcase is customary for Java variable declarations(ex: String userName;) -Depending on the programming language, it depends on whether the result of division between integers is returned as an integer or a real number.
• C,Java logical operators are "&&」「||」 -Python logical operators are "and" and "or" -Else if in Python is written as "el if" -There is no switch statement in Python!
• Python,There is no increment decrement in Ruby! -Defining multiple methods with the same method name is called overloading.(Thank you for pointing out, chitoku!) -In Ruby, all values such as strings and numbers are "objects", and each object has "data" and "method".