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