The if statement consists of an expression and a statement or a block of statements that are executed if the expression evaluates to true:

Guitar guitar = new Guitar();
guitar.addProblemItem("Whammy bar");
if (guitar.isBroken()) {
  Luthier luthier = new Luthier();
  luthier.repairGuitar(guitar);
}

When using else with if, the first block of statements is executed if the expression evaluates to true; otherwise, the block of code in the else is executed:

CoffeeShop coffeeshop = new CoffeeShop();
if (coffeeshop.getPatronCount() > 5) {
  System.out.println("Play the event.");
} else {
  System.out.println("Go home without pay.");
}

if else if is typically used when you need to choose among multiple blocks of code. When the criteria are not met to execute any of the blocks, the block of code in the final else is executed:

ArrayList<Song> playList = new ArrayList<>();
Song song1 = new Song("Mister Sandman");
Song song2 = new Song("Amazing Grace");
playList.add(song1);
playList.add(song2);
...
int numOfSongs = playList.size();
if (numOfSongs <= 24) {
  System.out.println("Do not book");
} else if ((numOfSongs > 24) & (numOfSongs < 50)){
  System.out.println("Book for one night");
} else if ((numOfSongs >= 50)) {
  System.out.println("Book for two nights");
} else {
  System.out.println("Book for the week");
}

The switch statement is a control flow statement that starts with an expression and transfers control to one of the case statements based on the value of the expression. A switch works with char, byte, short, int, as well as Character, Byte, Short, and Integer wrapper types; enumeration types; and the String type. Support for String objects was added in Java SE 7. The break statement is used to exit out of a switch statement. If a case statement does not contain a break, the line of code after the completion of the case will be executed.

This continues until either a break statement is reached or the end of the switch is reached. One default label is permitted and is often listed last for readability:

String style;
String guitarist = "Eric Clapton";
...
switch (guitarist) {
  case "Chet Atkins":
    style = "Nashville sound";
    break;
  case "Thomas Emmanuel":
    style = "Complex fingerstyle";
    break;
  default:
    style = "Unknown";
    break;
}

The for statement contains three parts: initialization, expression, and update. As shown next, the variable (i.e., i) in the statement must be initialized before being used. The expression (i.e., i<bArray.length) is evaluated before iterating through the loop (i.e., i++). The iteration takes place only if the expression is true and the variable is updated after each iteration:

Banjo [] bArray = new Banjo[2];
bArray[0] = new Banjo();
bArray[0].setManufacturer("Windsor");
bArray[1] = new Banjo();
bArray[1].setManufacturer("Gibson");
for (int i=0; i<bArray.length; i++){
  System.out.println(bArray[i].getManufacturer());
}

The enhanced for loop, a.k.a. the “for in” loop and “for each” loop, is used for iteration through an iterable object or array. The loop is executed once for each element of the array or collection and does not use a counter, as the number of iterations is already determined:

ElectricGuitar eGuitar1 = new ElectricGuitar();
eGuitar1.setName("Blackie");
ElectricGuitar eGuitar2 = new ElectricGuitar();
eGuitar2.setName("Lucille");
ArrayList <ElectricGuitar> eList = new ArrayList<>();
eList.add(eGuitar1); eList.add(eGuitar2);
for (ElectricGuitar e : eList) {
  System.out.println("Name:" + e.getName());
}

In a while statement, the expression is evaluated and the loop is executed only if the expression evaluates to true. The expression can be of type boolean or Boolean:

int bandMembers = 5;
while (bandMembers > 3) {
  CoffeeShop c = new CoffeeShop();
  c.performGig(bandMembers);
  Random generator = new Random();
  bandMembers = generator.nextInt(7) + 1; // 1-7
}

In a do while statement, the loop is always executed at least once and will continue to be executed as long as the expression is true. The expression can be of type boolean or Boolean:

int bandMembers = 1;
do {
  CoffeeShop c = new CoffeeShop();
  c.performGig(bandMembers);
  Random generator = new Random();
  bandMembers = generator.nextInt(7) + 1; // 1-7
} while (bandMembers > 3);

An unlabeled break statement is used to exit the body of a switch statement or to immediately exit the loop in which it is contained. Loop bodies include those for the for loop, enhanced for loop, while, and do-while iteration statements:

Song song = new Song("Pink Panther");
Guitar guitar = new Guitar();
int measure = 1; int lastMeasure = 10;
while (measure <= lastMeasure) {
  if (guitar.checkForBrokenStrings()) {
    break;
  }
  song.playMeasure(measure);
  measure++;
}

A labeled break forces a break of the loop statement immediately following the label. Labels are typically used with for and while loops when there are nested loops and there is a need to identify which loop to break. To label a loop or a statement, place the label statement immediately before the loop or statement being labeled, as follows:

...
playMeasures:
while (isWithinOperatingHours()) {
  while (measure <= lastMeasure) {
    if (guitar.checkForBrokenStrings()) {
      break playMeasures;
    }
    song.playMeasure(measure);
    measure++;
  }
} // exits to here

When executed, the unlabeled continue statement stops the execution of the current for loop, enhanced for loop, while, or do-while statements and starts the next iteration of the loop. The rules for testing loop conditions apply. A labeled continue statement forces the next iteration of the loop statement immediately following the label:

for (int i=0; i<25; i++) {
  if (playList.get(i).isPlayed()) {
    continue;
  } else {
    song.playAllMeasures();
  }
}

The return statement is used to exit a method and return a value if the method specifies to return a value:

private int numberOfFrets = 18; // default
...
public int getNumberOfFrets() {
  return numberOfFrets;
}

The return statement will be optional when it is the last statement in a method and the method doesn’t return anything.