A copy of this dictionary will be provided for the final exam.
| Meaning | Python | Java |
|---|---|---|
| Spelling for class names | Upper Camel Casing | Upper Camel Casing |
| Spelling for variable names | Underscore Notation or Lower Camel Casing (but be consistant) | Lower Camel Casing |
| Comment | # | // /* ... */ |
| Addition, concatenation | + | + |
| Subtraction | - | - |
| Multiplication | * | * |
| Division | / | / |
| Mod (Remainder from integer division) | % | % |
| Is equal? | == | == |
| Is greater to? | > | > |
| Is less than? | < | < |
| Is greater than or equal to? | >= | >= |
| Is less than or equal to? | <= | <= |
| Is not equal to? | != | != |
| Logical and | and | && |
| Logical or | or | || |
| Assignment operators | = += -= *= /= | = += -= *= /= |
| Increment operator | n += 1 | n++ |
| Decrement operator | n -= 1 | n-- |
| Print to standard out (screen) | print(n) print(n, end=" ") | System.out.println(n); System.out.print(n); |
| Scanner Import Statement | import java.util.Scanner; | |
| Read from standard in (keyboard) | t = input("Enter a string:") |
Scanner s = new Scanner(System.in); t = s.nextLine( ); |
| Import Statements for File IO | import
java.util.Scanner; import java.io.*; | |
| Read from file | fin = open("input.txt") line = fin.readline( ) while line != "": ... line = fin.readline( ) |
Scanner s = new Scanner( new File("input.txt")); while(s.hasNextLine( )) { t = s.nextLine( ); ... } |
| Exit from program | import sys sys.exit( ) | System.exit(0); |
| Import external module | import sqlite3 from random import randrange |
import java.util.Scanner; import java.util.Random; import java.io.*; |
| Convert to integer | n = int(s) | int n = Integer.parseInt(s); |
| Convert to floating point | x = float(s) |
double n =
Double.parseDouble(s); |
| If..else statements | if condition1: action1 elif condition2: action2 else: action3 | if (condition1) { action1; } else if (condition2) { action2; } else { action3; } |
| While statement | n = 1 while n <= 10: print(n, end=" ") n += 1; | int n = 1; while (n <= 10) { System.out.print( n + " "); n++; } |
| Traditional for statement | for n in range(0, 10): print(n, end=" ") | for(int n = 0; n <= 10; n++) { System.out.print( n + " "); } |
| Short array definition | a = [2, 5, 3, 4] | int[ ] a = {2, 5, 3, 4}; |
| Long array definition | a = Array( ) a.append(2) ... a.append(4) | int[ ] a = int[4]; a[0] = 2; ... a[999] = 4; |
| Array access | n = a[4] a[4] = 352 | n = a[4]; a[4] = 352; |
| Modern for each statement (Access array by index) |
for n in a: print n, " " | for(int n : a) { System.out.print( n + " "); } |
| Class definition | class Card: ... | public class Card { ... } |
| Instance variable declarations | Instance variables not declared. They are prefixed by self: self.rank self.suit |
public int rank; public String suit; |
| Constructor definition | # Constructor is
created by # compiler, but calls # __init__ method: def __init__(self, r, s) rank = r suit = s end | public Card(int r, String s) { rank = r; suit = s; } |
| Constructor invocation | c = Card(r, s) | Card c = new Card(r, s); |
| toString method definition | def
__init__(self): return "{self.name}" + \ {self.age}" | public String toString( ) { return name + " " + age; } |
| toString method invocation | p =
Person("Alice", 11) print(str(p)) # or print(p) |
Person p = new Person("Alice", 11); System.out.println(p. toString( )); // or System.out.println(p); |
| Instance Method Definition | def
have_birthday(self): self.age += 1; |
public void haveBirthday( ) { age++; } |
| Instance method invocation | p =
Person("Alice", 11) p.have_birthday( ) |
Person p = new Person("Alice", 11); p.haveBirthday( ); |