What is an if statement? An if statement is used to specify a block of Java code to be executed if a condition is true.

if-else

  • Uses keyword “if”
  • Checks if statement is true
  • If it is, performs certain task
  • if not, performs else command

if-else-else Use the else if statement to specify a new condition if the first condition is false.

Conditionals: allows the computer to make decisions based on if a statement is true or false

  • If
  • Else
  • Else If
  • Booleans
if (3.14 > 1.5) { //the program decides whether this is true or not
    System.out.println("3.14 is greater than 1.5"); //if it is then this line is printed
  }

3.14 is greater than 1.5

What is an if/else statement? The if/else statement executes a block of code if a specified condition is true. If the condition is false, another block of code can be executed.

int time = 12; //set variable
if (time < 12) { //the program decides whether this is true or not
  System.out.println("Good day."); //if it is then print this line
} else {
  System.out.println("Good evening."); //if it is not then print this
}

Good evening.

What is an If-else-else Statement?

int time = 12;
if (time < 12) { //the program decides whether this is true or not
  System.out.println("Good morning."); //if it is then print this line
} else if (time < 20) { //if it is not true, then check if this is true
  System.out.println("Good day."); //if it is then print this line
} else {
  System.out.println("Good night."); //or else print this line
}

Good day.

if (1 > 2) {
    System.out.println("3.14 is greater than 1.5");
  }
  else if(3 < 1.5) {
    System.out.println("3.14 is less than 1.5");
  }
  else if (7 > 8) {
    System.out.println("8 is greater than 7");
  }
  else if (6 < 8) {
    System.out.println("7 is less than 8");
  }
  else {
    System.out.println("Invalid");
  }

7 is less than 8

What is a Switch Case Program in Java? Java switch statement executes one statement from multiple conditions.

  • The switch statement evaluates an expression, matching the expression's value against a series of case clauses, and executes statements after the first case clause with a matching value, until a break statement is encountered. The default clause of a switch statement will be jumped to if no case matches the expression's value.
Scanner input = new Scanner(System.in);
System.out.print("Enter first number- ");  
String something = input.nextLine();  // Read user input
System.out.println(something);
Scanner sc= new Scanner(System.in); 
int x= sc.nextInt();  
String output;
switch (x) { 
    case 1:
        output = x + " > 0";
        break;
    case 2:
        output = x + " > 8";
        break;
    case 3:
        output = x + " > 3";
        break;
    case 4:
        output = x + " > 6";
        break;
}
System.out.println(output)

Enter first number- 5
3 > 3

De Morgan's Law The complement of the union of two sets is the intersection of their complements and the complement of the intersection of two sets is the union of their complements.

|| means "or" and the && means "and" ! = not

boolean playBasketball = false;
boolean playBaseball = true;

if (!(playBaseball && playBasketball)){
    System.out.println("I play baseball but not basketball");
}
else{
    System.out.println("I play basketball but not baseball");
}

I play baseball but not basketball

boolean playBasketball = false;
boolean playBaseball = true;

if (!playBaseball||!playBasketball){
    System.out.println("I play basketball but not baseball");
}
else{
    System.out.println("I play baseball but not basketball");
}

I play basketball but not baseball