Arrays

• list of values containing the same data type

• 0 based

• C++ has static and dynamic arrays

• Java treats its arrays like objects. You delcare a reference, meaning no size can be specified until specified.

Using Arrays

• has length attribute

Bounds Checking

• Java does automatic run time bounds checking for all array index operations
• C/C++ can't do that because it will sef gault
• Downside? Efficiency suffers, checking every sincel array index a run-time takes a while

Assigning Array References

• Assigning one reference to another results in both references referring to the same object
• Arrays are NOT an ecepton

Cloning an Array

• If you want an array ference to refer to an array object that is a copy of another array obeject, can use clone
• Cloning causes a new object

• Int is a generic function that can be used on any objec, therfore, its return value msut be cast

• To copy elements fo an array into an array object that has already been allocated:

  • Use a for loop or
  • Use System.arrayCopy(, );

int [] squareVals;
int [] arrayRef;
int [] anotherCopy;

// Don't have to allocate memory, clone automatically creates new memory
arrayRef = (int [])squareVals.clone();

// arraycopy requires memoy to be already allocated.
anotherCopy = new int[5];
System.arraycopy(squareVals, 0, anotherCopy, 0, 5);

Arrays of Objects

• No such thing in Java there are only arrays of object references.
• Even when you use new to allocate space for an array object, you have to only allocated object references
• You must use new on each array element to actually allocate an object

Multidimensional Arrays

• No such thing in Java
• To use a 2d array, you use a 1D array where each element refers to a 1D array. Each individual 1d array can be a different size
• Allocate mutli-dimensional arrays

  twoDAry = new int[10][60];
  

• One dimension at a time, starting with the left more dimension first

  twoDAry = new int[10][];
  for(int i = 0; i < toDAry.length; i)
  {
  twoDAry[i] = new int[60];
  }