Control Flow

if-then

if (condition1) {
    statement1;
} else if (statement2) {
    statement2;
} else {
    statement3;
}

while

You can implement an infinite loop using the while statement as follows:

while (true){
    // your code goes here
}

The Java programming language also provides a do-while statement, which can be expressed as follows:

do {
     statement(s)
} while (expression);

for

for (initialization; termination; increment) {
    statement(s)
}

When using this version of the for statement, keep in mind that:

The initialization expression initializes the loop; it's executed once, as the loop begins.
When the termination expression evaluates to false, the loop terminates.
The increment expression is invoked after each iteration through the loop; it is perfectly acceptable for this expression to increment or decrement a value.

Branching

break

The break statement has two forms: labeled and unlabeled.

An unlabeled break statement terminates the innermost switch, for, while, or do-while statement,
but a labeled break terminates an outer statement.

continue

The continue statement skips the current iteration of a for, while , or do-while loop.

The unlabeled form skips to the end of the innermost loop's body and evaluates the boolean expression that controls the loop.
A labeled continue statement skips the current iteration of an outer loop marked with the given label.

return

The return statement exits from the current method, and control flow returns to where the method was invoked.

https://docs.oracle.com/javase/tutorial/java/nutsandbolts/flow.html

switch

A switch works with the byte, short, char, and int primitive data types. It also works with enumerated types, the String class, and a few special classes that wrap certain primitive types: Character, Byte, Short, and Integer.

int month = 8;
String monthString;
switch (month) {
   case 1:  monthString = "January";
            break;
   case 2:  monthString = "February";
            break;
   case 3:  monthString = "March";
            break;
   case 4:  monthString = "April";
            break;
   case 5:  monthString = "May";
            break;
   case 6:  monthString = "June";
            break;
   case 7:  monthString = "July";
            break;
   case 8:  monthString = "August";
            break;
   case 9:  monthString = "September";
            break;
   case 10: monthString = "October";
            break;
   case 11: monthString = "November";
            break;
   case 12: monthString = "December";
            break;
   default: monthString = "Invalid month";
            break;
}
System.out.println(monthString);

The body of a switch statement is known as a switch block. A statement in the switch block can be labeled with one or more case or default labels.

danger

Each break statement terminates the enclosing switch statement. Control flow continues with the first statement following the switch block. The break statements are necessary because without them, statements in switch blocks fall through: All statements after the matching case label are executed in sequence, regardless of the expression of subsequent case labels, until a break statement is encountered.

java.util.ArrayList<String> futureMonths = new java.util.ArrayList<String>();

int month = 8;

switch (month) {
    case 1:  futureMonths.add("January");
    case 2:  futureMonths.add("February");
    case 3:  futureMonths.add("March");
    case 4:  futureMonths.add("April");
    case 5:  futureMonths.add("May");
    case 6:  futureMonths.add("June");
    case 7:  futureMonths.add("July");
    case 8:  futureMonths.add("August");
    case 9:  futureMonths.add("September");
    case 10: futureMonths.add("October");
    case 11: futureMonths.add("November");
    case 12: futureMonths.add("December");
             break;
    default: break;
}

if (futureMonths.isEmpty()) {
    System.out.println("Invalid month number");
} else {
    for (String monthName : futureMonths) {
       System.out.println(monthName);
    }
}

// This is the output from the code:

August
September
October
November
December

int month = 2;
int year = 2000;
int numDays = 0;

switch (month) {
    case 1: case 3: case 5:
    case 7: case 8: case 10:
    case 12:
        numDays = 31;
        break;
    case 4: case 6:
    case 9: case 11:
        numDays = 30;
        break;
    case 2:
        if (((year % 4 == 0) && 
             !(year % 100 == 0))
             || (year % 400 == 0))
            numDays = 29;
        else
            numDays = 28;
        break;
    default:
        System.out.println("Invalid month.");
        break;
}
System.out.println("Number of Days = " + numDays);

if-then#

while#

for#

Branching#

break#

continue#

return#

switch#