- Discuss repetition concepts
- Use repetition in Java to solve problems
- Create for loops in Java
- Create while loops in Java
- Create do/while loops in Java
- Types of loops in Java:
- while
- do/while
- for (traditional style)
- for (new style: iterate over collections, called for-each loops)
- loop counters: use to keep track of how many times a loop iterates
- initialize counter before loop starts
- test counter to see if loop continues
- modify counter just before end of loop
- sentinel values: a special value read in an input loop which triggers special (often terminal) processing
- pre-test loop: the test to see if the loop should continue happens at the start of the main loop code
- post-test loop: the test to see if the loop should continue happens at the end of the main loop code
- accumulators: variables used to add up values
- sum (initialize accumulator to 0)
- product (initialize accumulator to 1)
- break: causes a loop to end
- continue: causes the loop to skip to the next iteration
- priming read: a read of input data before a loop starts to determine whether the loop should execute at all; it is repeated right before the end of the loop
- A "for" loop counting from 1 to 10:
for (int i = 1; i <= 10; i++) {
System.out.println(i);
}
- A "while" loop counting from 1 to 10:
int i = 1;
while (i <= 10) {
System.out.println(i);
i++;
}
- A "do/while" loop counting from 1 to 10:
int i = 1;
do {
System.out.println(i);
i++;
} while (i <= 10);
- A "for" loop summing the odd numbers between 10 and 20:
int sum = 0;
for (int i = 11; i <= 20; i = i + 2) {
sum = sum + i;
}
- A "while" loop summing the odd numbers between 10 and 20:
int sum = 0;
int i = 11;
while (i <= 20) {
sum = sum + i;
i = i + 2;
}
- A "do/while" loop summing the odd numbers between 10 and 20:
int sum = 0;
int i = 11;
do {
sum = sum + i;
i = i + 2;
} while (i <= 20);
- A loop with a priming read that multiplies numbers entered until 0 is entered:
java.util.Scanner kbd = new java.util.Scanner(System.in);
int product = 1;
System.out.print("Enter an integer (0 to end): ");
int i = kbd.nextInt();
while (i != 0) {
product = product * i;
System.out.print("Enter another integer (0 to end): ");
i = kbd.nextInt();
}
- A "for" loop that displays all the command line arguments:
for (String s : args) {
System.out.println(s);
}