Chapter 7

Question 1

Arrays & for-each loop

Answer 1

for(int value : hourCounts){
System.out.println(“ : “ + value);
}
Arrays can be used with for-each loop but it doesn’t provide access to a loop counter variable thus old for-loop is preferred

Question 2

Which loop should you use?

Answer 2

• for-each loop to iterate over all elements in a collection
• for loop when you know how many iterations you will need @ the start of the loop
• while loop when you don’t know how many iterations @ the start of the loop
• If you need to remove elements from a collection whilst examining the whole collection, use a for loop w an iterator - or a while loop if you might want to finish before the end of the collection

Question 3

Conditional operator

Answer 3

• choose b/t 2 values
  condition? value 1 : value 1

for(int cellValue state){
System.out.print(cellValue == 1 ? ‘+’ : ‘ ‘);
}
System.out.println();

Question 4

lookup tables

Answer 4

• HashMap - class allows associations to be created b/t objects in the form of (key, value) pair
• Arrays can implement specialized lookup tables
• We can illustrate the concept of a lookup table via cellular automaton

Question 5

Array initialiser

Answer 5

• A list of the values to be stored in a newly-created array
• size does not need to be specified in [] of new int[]
  A state table can be set up as follows:
  int[] StateTable = new int[]{
  0, 1, 0, 0, 1, 0, 0, 1,
  };

Question 6

Arrays of more than one dimension

Answer 6

• array syntax supports multiple dimensions
• think array of arrays
• declaring an array variable of 1+ dimension:
  Cell [] [] cells;
• creation of array object
  cells = new Cell [numRows] [numCols];

Question 7

Setting up 2D arrays

Answer 7

cells = new Cell[numRows][numCols];
for(int row = 0; row < numRows; row++) {
for (int col = 0; col < numCols; col++) {
cells[row][col] = new Cell();
}
}
setupNeighbors();