1D Arrays

Recap

• User Input

• Conditionals

  • if-statement

  • Nested if-statements

  • switch-case statements

• Loops

  • while loop

  • do-while loop

  • for loop

Arrays

Array

• Indexed sequence of values of the same type

• Example:

  • 52 playing cards in a deck

  • 1 million characters in a book

  • 130 students in this course sorted by their ID

https://docs.oracle.com/javase/tutorial/java/nutsandbolts/arrays.html

Many Variables of Same Type

Goal: 10 variables of type int

Many Variables of Same Type

Goal: 10 variables of type int

Declares, creates, and initializes values

Arrays in java

• To make an array, declare, create and initialize it.​

• To access element 'i' of an array named ‘a’, use a[i].​

• Array indices start at 0.

Example

compact alternative

• Declare, create, and initialize in one statement.

• Default initialization: all numbers automatically set to 0.

Explicit Initialization

• Example

• Equivalent to

Demo

Dot product of two vectors

Length of the array

• We can get the length of the array using the length field:

• Can be used for iteration over array elements

Consider

​

• Defined an array to reference a list of 100 integers
• Each element is initialized by default to 0
• Two exceptions will be thrown here:
  • -1 is not a valid index – too small
  • 100 is not a valid index – too large
    • IndexOutOfBoundsException

Due soon

• program 1 tonight
• no class Monday
• 5.9, 5.10 Wednesday
• 2.14,3.12-3.15,4.6 Friday