Uses of selection in programming (if, switch etc)
There are endless examples that illustrate selection. As you know, most useful programs have at least one selection statement. I've found that some students struggle with the concept, so I start small and pick examples that resonate with students, for example:

    if (hungry)
        System.out.println("Eat a sandwich.");

    if (age &gt; 17)
        System.out.println("You can vote.");
    else
        System.out.println("You cannot vote.");


For a switch statement, I like to show some type of menu:

    switch(choice) {
    case 0:
        System.out.println("Balance Inquiry.");
        break;
    case 1:
        System.out.println("Transfer");
        break;
    case 2:
        System.out.println("Withdrawal");
        break;  
    case 3:
        System.out.println("Deposit");
        break;          
    default:
        System.out.println("Quit");
        break;          
    }