Java: Chapter 4 Arrays

What is the focus of Chapter 4?

Understanding one-dimensional and two-dimensional arrays in Java through the Conway’s Game of Life project.

What is an array?

A fixed-size, ordered collection of elements of the same type stored in contiguous memory.

How do you declare a one-dimensional array in Java?

type[] arrayName = new type[size];

How can an array be initialized at declaration?

type[] nums = {1, 2, 3, 4, 5};

What is the index of the first element in a Java array?

0

What happens if you access an index outside an array’s range?

A java.lang.ArrayIndexOutOfBoundsException is thrown.

How do you get an array’s length?

arrayName.length

How can you loop through all elements in an array?

Use a for loop or an enhanced for loop (for each element : array).

What does it mean to “modify an array in a method”?

Arrays are passed by reference — changes inside the method affect the original array.

How do you copy an array manually?

Use a loop to assign each element or use Arrays.copyOf().

What library provides array utility methods?

java.util.Arrays

What does Arrays.toString() do?

Converts the array contents to a human-readable string.

How do you compare two arrays for equality?

Use Arrays.equals(array1, array2);

How do you fill an array with a single value?

Use Arrays.fill(arrayName, value);

What is a two-dimensional array?

An array of arrays used to represent tables or grids.

How do you declare a two-dimensional array?

type[][] matrix = new type[rows][cols];

What are “ragged arrays”?

Arrays where rows can have different lengths (an array of arrays with unequal sizes).

How do you iterate through all elements of a 2D array?

Nested loops — outer for rows, inner for columns.

What are the typical operations done on 2D arrays?

Initialization, access, updating elements, searching, and computations such as sums or averages.

What algorithmic project uses 2D arrays in this chapter?

Conway’s Game of Life – a cellular automaton simulation.

What are the key rules in Conway’s Game of Life?

A cell survives if it has 2 or 3 neighbors, dies with fewer or more, and a dead cell with exactly 3 neighbors becomes alive.

Why is Conway’s Game of Life important in CS?

It illustrates emergent behavior and array-based state updates in simulation models.

What does each array element represent in Game of Life?

A cell state (0 for dead, 1 for alive).

How are successive generations computed in the simulation?

By creating a new array based on the rules applied to each cell’s neighbors.

What are “neighborhoods” in cellular automata?

The set of adjacent cells that influence a cell’s next state.

How does paint(Graphics g) relate to array visualization?

It draws cells on a Canvas based on the values stored in the array.

What are the learning objectives of this chapter?

To understand array declaration, indexing, iteration, modification, and their application in graphical projects.