Arithmetic Operators

Prefix vs. Postfix

int a = 5;
int b = ++a;  // a=6, b=6
int c = a++;  // c=6, a=7

String Concatenation

String s = "score:" + 100;  // "score:100"

Assignment Operators

+= -= *= /= %= all preserve the left-hand variable’s type and perform implicit casting.

byte b = 10;
b += 5;   // compiles; same as b = (byte)(b + 5);

Relational Operators

== != > < >= <= instanceof yield boolean.

Account a1 = new Account(1000);
Account a2 = new Account(1000);
boolean same = (a1 == a2);  // false, different objects

Logical Operators

Bitwise Operators

Operate on integral types.

int n = 8;      // 1000
int m = n << 2; // 32  (100000)

Ternary Operator

condition ? expr1 : expr2

int abs = (x >= 0) ? x : -x;

Prefer the ternary operator over simple if-else when readability is not sacrificed.

Reading Input

import java.util.Scanner;
Scanner sc = new Scanner(System.in);
int age = sc.nextInt();
String name = sc.next();

Random Integers

Generate an integer in [a, b]:

int value = (int)(Math.random() * (b - a + 1)) + a;

Control-Flow Examples

Combining Logical Operators

public class LogicDemo {
    public static void main(String[] args) {
        int z = 40;
        boolean x = true;
        boolean y = false;

        if ((z++ == 40) && (y = true)) { z++; }      // z=42
        if ((x = false) || (++z == 43)) { z++; }     // z=44
        System.out.println("z = " + z);              // 44
    }
}

Maximum of Three Numberss

int a = 10, b = 21, c = -21;
int max = (a >= b && a >= c) ? a :
          (b >= a && b >= c) ? b : c;
System.out.println("max = " + max);

Conditional Sum or Product

double x = 12.3, y = 32.1;
System.out.println(
    (x > 10.0 && y < 20.0) ? (x + y) : (x * y)
);

Swapping Two Variables

String drink1 = "Sprite";
String drink2 = "Cola";
String temp = drink1;
drink1 = drink2;
drink2 = temp;