Looping/Iterating

• Looping/Iterating

  • What

  • While

  • Do While

  • For

    • Old/basic

    • New/enhanced

  • break statement

  • continue statement

  • Recursion

  • Nested loops

    • Links

  • for

  • while

  • do while

  • break, continue

  • Nested loops

  • other

What

• Repeating the same task

• Doing the same thing across a data structure

• for/while/do while (imperative)

While

• Format

while(booleanExpression) {
  //body
}

• need to ensure that loop is terminated

  • what the booleanExpression is for

  • Can make booleanExpression = true, and loop will be infinite

    • but have a break in the body to exit the loop

Do While

• Format -

  do {
  //body
  } while(booleanExpression)

• similar to while loop, but always does one execution of the body first.

For

Old/basic

• Format -

  for(initialization; booleanExpression; updateStatement) {
  //body
  }

• Not good for functional style as initialization has mutated variable.

• initialization can declared in the loop, and has scope just for the for loop.

  • Can declared outside of loop, initialized in loop and thus have scope inside nad outside of loop

  • If declared and init outside of loop, but reinit inside for loop, error will occur

• Inifinite loop for(;;) { // body }

• All components in for loop are optional

• Can have multiple initialization statements, booleanExpressions and updateStatements

  • Must have same data type in initialization

New/enhanced

• aka for-each loop

  -format

for (datatype instance : collection) {
  //body...
}

• collection must implement Iterable interface

  -

break statement

• using a label (which is optional)

aLabel: while (x > 5) {
  // some logic
  while (x.isEven) {
    // some logic
    break aLabel;
  }
}

• This will break out of the top level loop instead of inner loop where the break is set.

  • used in while/do while/switch/ for

continue statement

• finishes the flow of the current loop.

• Uses the same syntaz as that of break when using optional lables

• used in while/do while/for

Recursion

• stackoverflow exception

Nested loops

Links

for

• https://docs.oracle.com/javase/tutorial/java/nutsandbolts/for.html
• https://www.javatpoint.com/java-for-loop
• https://www.tutorialspoint.com/java/java_for_loop.htm

while

• https://www.javatpoint.com/java-while-loop
• https://docs.oracle.com/javase/tutorial/java/nutsandbolts/while.html
• https://www.tutorialspoint.com/java/java_while_loop.htm

do while

• https://www.javatpoint.com/java-do-while-loop
• https://www.tutorialspoint.com/java/java_do_while_loop.htm

break, continue

• https://www.javatpoint.com/java-break
• https://www.javatpoint.com/java-continue

Nested loops

• https://www.programiz.com/java-programming/nested-loop

other

• https://stackoverflow.com/questions/8880870/java-for-vs-whiletrue

  -