Java and Python basic grammar comparison

Introduction

I compared the basic grammars of Java and Python. I would appreciate it if you could point out if the Java grammar is dirty or if there are any differences!

table of contents#

[1. Output](# 1 output) [2. Variable](# 2 variable) [3. Combining strings and numbers](# 3 Combining strings and numbers) [4.if statement](# 4if statement) [5.for statement](# 5for statement) [6.while statement](# 6while statement) [7. break, continue with for and while](break-continue with # 7 for and while) 8.list [9. Dictionary](# 9 dictionary)

1. Output

python

print('123')
print(123)
>>>123
>>>123

java

public class Main {
    public static void main(String[] args){
        
        System.out.println("123");
        System.out.println(123);
    }
}
>>>123
>>>123

2. Variable

python

mystr = 'hello'
myint = 123
print(mystr)
print(myint)
>>>hello
>>>123

java

public class Main {
    public static void main(String[] args){
        
        String mystr = "hello";
        int myint = 123;
        
        System.out.println(mystr);
        System.out.println(myint);
    }
}
>>>hello
>>>123

3. Combining strings and numbers

python

myint = 123
print('The numbers are' + str(myint))
>>>The number is 123

java

public class Main {
    public static void main(String[] args){
        
        int myint = 123;
        System.out.println("The numbers are" + myint);
    }
}
>>>The number is 123

4. if statement

python

myint = 10
if myint == 10:
    print('myint is 10')
>>>myint is 10

java

public class Main {
    public static void main(String[] args){
        
        int myint = 10;
        if(myint == 10){
            System.out.println("myint is 10");
        }
    }
}
>>>myint is 10

5. for statement

python

for char in 'Hello':
    print(char)
>>>H
>>>e
>>>l
>>>l
>>>o

java

//split and extended for statement
public class Main {
    public static void main(String[] args){
        
        String mystr = "hello";
        String[] strArray = mystr.split("");
        for(String s : strArray) {
	        System.out.println(s);
            }
    }
}

//charAt and for statement
public class Main {
    public static void main(String[] args){
        
        String mystr = "hello";
        for(int i = 0; i < mystr.length(); i++) {
	        System.out.println(mystr.charAt(i));
            }
    }
}

>>>h
>>>e
>>>l
>>>l
>>>o

・ Loop ### for the specified number of times

python

for i in range(3):
    print(i)
>>>0
>>>1
>>>2

java

public class Main {
    public static void main(String[] args){
        
    for(int i = 0; i < 3; i++) {
        System.out.println(i);
        }
    }
}
>>>0
>>>1
>>>2

-List and array loop processing

python

list = ['item1', 'item2', 'item3']
for item in list:
    print(item)
>>>item1
>>>item2
>>>item3

java

public class Main {
    public static void main(String[] args){
        
        String[] list = {"item1", "item2", "item3"};
        for(int i = 0; i <list.length; i++){
            System.out.println(list[i]);
        }
    }
}
>>>item1
>>>item2
>>>item3

6. While statement

python

val = 0
while val < 4:
    val += 1
    print(val)
print('val is' + str(val))
>>>1
>>>2
>>>3
>>>4
>>>val is 4

java

public class Main {
    public static void main(String[] args){
        
        int val = 0;
        while(val < 4){
            val++;
            System.out.println(val);
        }
        System.out.println("val is" + val);
    }
}
>>>1
>>>2
>>>3
>>>4
>>>val is 4

7. break, continue with for and while

・ Break ### in for statement

python

list = [1,2,3,4,5]
for i in list:
    if i == 3:
        break
    print(i)
>>>1
>>>2
>>>Repeat processing ends with break

java

public class Main {
    public static void main(String[] args){
        
        int[] list = {1,2,3,4,5};
        for(int i = 1; i < list.length; i++){
            if(i == 3){
                break;
            }
            System.out.println(i);
        }
    }
}
>>>1
>>>2
>>>Repeat processing ends with break

・ Break ### with while statement

python

val = 1 
while val < 10:
    if val == 3:
        break 
    print(val)
    val += 1
>>>1
>>>2
>>>Repeat processing ends with break

java

public class Main {
    public static void main(String[] args){
        
        int val = 1;
        while(val < 10){
            if(val == 3){
                break;
            }
            System.out.println(val);
            val++;
        }
    }
}
>>>1
>>>2
>>>Repeat processing ends with break

・ Continue ### in the for statement

python

#continue with a for statement
list = [1,2,3,4,5]
for i in list:
    if i == 2:
        continue
    print(i)
>>>1
>>>3
>>>4
>>>5

java

public class Main {
    public static void main(String[] args){
        
        int[] list = {1,2,3,4,5};
        for(int i = 1; i < list.length+1; i++){
            if(i == 2){
                continue;
            }
            System.out.println(i);
        }
    }
}
>>>1
>>>3
>>>4
>>>5

・ Continue ### with a while statement

python

val = 0
while val < 5:
    val += 1
    if val == 2:
        continue
    print(val)
>>>1
>>>3
>>>4
>>>5

java

public class Main {
    public static void main(String[] args){
        
        int val = 1;
        while(val < 6){
            if(val == 2){
                val++;
                continue;
            }
            System.out.println(val);
            val++;
        }
    }
}
>>>1
>>>3
>>>4
>>>5

8.list# In python, lists play the role of arrays.

python

list = ['a','b','c']
print(list)
>>>['a','b','c']

In Java, you can't get all the contents of the list at once, so you need to call them one by one using for.

java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main {
    public static void main(String[] args){
        
        List<String> list = new ArrayList<String>(Arrays.asList("a", "b", "c"));
        
        for(int i = 0; i < list.size(); i++) {
            System.out.println(list.get(i));
        }
    }
}
>>>a
>>>b
>>>c

-Reference the elements in the list

python

list = ['a','b','c']
#First element
print(list[0])
#Second element
print(list[2])
>>>a
>>>c

java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main {
    public static void main(String[] args){
        
        List<String> list = new ArrayList<String>(Arrays.asList("a", "b", "c"));
        //First element
        System.out.println(list.get(0));
        //Second element
        System.out.println(list.get(2));
    }
}
>>>a
>>>c

-Adding a value to the list

python

list = ['a','b','c']
#Add to the end
list.append('d')
#Add to specified position
list.insert(2, 'd')

print(list)
>>>['a','b','d','c','d']

java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main {
    public static void main(String[] args){

        List<String> list = new ArrayList<String>(Arrays.asList("a", "b", "c"));
        //Add to the end
        list.add("d");
        //Add to specified position
        list.add(2, "d");
    }
}
>>>{"a","b","d","c","d"}

-Remove value from list

python

list = ['a','b','c']
#Remove trailing element
list.pop()
#Delete the element at the specified position
list.pop(1)
print(list)

>>>['a']

java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main {
    public static void main(String[] args){

        List<String> list = new ArrayList<String>(Arrays.asList("a", "b", "c"));
        //Delete the element at the specified position
        list.remove(0);
    }
}
>>>{"b","c"}

・ Update list values

python

list = ['a','b','c']
list[1] = 'x'
print(list)
>>>['a','x','c']

java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main {
    public static void main(String[] args){

        List<String> list = new ArrayList<String>(Arrays.asList("a", "b", "c"));
        list.set(1,"x");
    }
}
>>>{"a","x","c"}

9. Dictionary, Map

python

dict = { 'apple':1, 'orange':2, 'banana':3 }
print(dict['apple'])
>>>1

java

import java.util.LinkedHashMap;

public class Main {
    public static void main(String[] args){

        LinkedHashMap<String, Integer> map = new LinkedHashMap<>() ;
            
        map.put("apple", 1);
        map.put("orange", 2);
        map.put("banana", 3);
            
        System.out.println(map);
        System.out.println(map.get("apple"));
    }
}
>>>{apple=1, orange=2, banana=3}
>>>1

I used LinkedHashMap this time because I wanted to keep the order.

** Map types and features ** LinkedHashMap: Hold in the order in which the keys are stored. TreeMap: Hold in ascending order of keys. HashMap: Do not keep order.

・ Update dictionary and Map values

python

dict = { 'apple':1, 'orange':2, 'banana':3 }
dict['apple'] = 5
print(dict)
>>>{ 'apple':5, 'orange':2, 'banana':3 }

java

import java.util.LinkedHashMap;

public class Main {
    public static void main(String[] args){

        LinkedHashMap<String, Integer> map = new LinkedHashMap<>() ;
            
        map.put("apple", 1);
        map.put("orange", 2);
        map.put("banana", 3);
        
        map.put("apple",5);
        System.out.println(map);
    }
}
>>>{apple=5, orange=2, banana=3}

-Delete dictionary and Map values

python

dict = { 'apple':1, 'orange':2, 'banana':3 }
del dict['apple'] 
print(dict)
>>>{'orange':2, 'banana':3 }

java

import java.util.LinkedHashMap;

public class Main {
    public static void main(String[] args){

        LinkedHashMap<String, Integer> map = new LinkedHashMap<>() ;
            
        map.put("apple", 1);
        map.put("orange", 2);
        map.put("banana", 3);
        
        map.remove("apple");
        System.out.println(map);
    }
}
>>>{orange=2, banana=3}

・ Confirmation of key existence

python

dict = { 'apple':1, 'orange':2, 'banana':3 }
if 'apple' in dict:
    print('Exists')
else:
    print('do not exist')
>>>Exists

java

import java.util.LinkedHashMap;

public class Main {
    public static void main(String[] args){

        LinkedHashMap<String, Integer> map = new LinkedHashMap<>() ;
            
        map.put("apple", 1);
        map.put("orange", 2);
        map.put("banana", 3);
        
        if(map.containsKey("apple")){
            System.out.println("Exists");
        }else{
            System.out.println("do not exist");
        }
    }
}
>>>Exists