1. JAC444: Intro to Java Arrays and Vectors Tim McKenna Seneca@York

2. Arrays in Java arrays are objects declare an array object reference  int[] iAr;String[] strAr; // i.e. type[] new creates an array object  specify the number of elements  iAr = new int[3]; strAr = new String[5];  auto initialization of array elements primitive types: zero value reference type: null

3. Arrays in Java length: public final instance variable iAr.length == 3; strAr.length == 5; compile-time or runtime assignment of array element values java.util.Arrays – utility methods to  copy, search, sort, fill, convert toString ArrayIndexOutBoundException Example: ArrayDemo.java, ArrayDemoStrings, ArrayDemoObjects

4. Two-Dimensional Arrays an array of arrays (i.e. an array of objects) an irregular / unbalanced array Examples: ArrayDemo2.java ArrayDemo3.java

5. Vector Class Java package: java.util, part of the Java Collection FrameworkJava Collection Framework vector: like an array that shrinks and grows vector stores generic object references ArrayList class is like a Vector but is not synchronized – less overhead for the JVM. must be synchronized to support Threads

6. Vector Class useful methods:  isEmpty(), size()  add(), remove(), insertElementAt()  get(), set()  methods using the object's equals() method: contains(), indexOf(), lastIndexOf(), remove() Examples: VectorDemoObjects.java, VectorDemoCars.java, ParkingLot.java, ParkingLotCars.java

7. Collections passing do not give out references to your collection – preserve encapsulation java.util.Collections.unmodifiableXXX  allows modules to provide users with "read-only" access to internal collections.