Lectures / lecture2_2

for Loop

while loop:

for loop:

for ( int counter = 0 ; counter < 4 ; counter++ ) {

Developing a for Loop

Syntax:

for (initialize[,initialize]; boolean_expression; update[,update]) {

code_block;

}

Example:

for (String i = "|", t = "------";

Topics

•Create a while loop

•Develop a for loop

•Nest a for loop and a while loop

•Use an array in a for loop

•Code and nest a do/while loop

•Compare loop constructs

Nested for Loop

Code:

int height = 4; int width = 10;

for (int rowCount = 0; rowCount < height; rowCount++ ) {

for (int colCount = 0; colCount < width; colCount++ ) { System.out.print("@");

}

System.out.println();

}

Nested while Loop

Code:

String name = "Lenny"; String guess = ""; int numTries = 0;

while (!guess.equals(name.toLowerCase())) { guess = "";

while (guess.length() < name.length()) {

char asciiChar = (char)(Math.random() * 26 + 97); guess = guess + asciiChar;

}

numTries++;

}

System.out.println(name + " found after " + numTries + " tries!");

Topics

•Create a while loop

•Develop a for loop

•Nest a for loop and a while loop

•Use an array in a for loop

•Code and nest a do/while loop

•Compare loop constructs

Loops and Arrays

One of the most common uses of loops is when working with sets of data.

All types of loops are useful:

•while loops (to check for a particular value

•for loops (to go through the entire array)

•Enhanced for loops

for Loop with Arrays

ages (array of int types)

ages[i] accesses array values as i goes from 0 to

ages.length – 1.

for (int i = 0; i < ages.length; i++ ) {

System.out.println("Age is " + ages[i] );

}

Setting Values in an Array

ages (array of int types)

Loop accesses each element of array in turn.

for (int i = 0; int < ages.length; i++ ) {

ages[i] = 10;

}

Each element in the array is set to 10.

Enhanced for Loop with Arrays

ages (array of int types)

for (int age : ages ) { System.out.println("Age is " + age );

}