12ArraysIntroLarge

# 12ArraysIntroLarge - Lecture Set#12 Arrays This lecture set...

This preview shows pages 1–4. Sign up to view the full content.

1 CMSC 131 Fall 2007 Jan Plane (adapted from Bonnie Dorr) Lecture Set #12: Arrays This lecture set: c Intro to arrays c Copying arrays and making arrays bigger c Array lengths and out-of-bounds indexing c Passing arrays and array elements to a function c Privacy Leaks c Different levels of copy CMSC 131 Fall 2007 Jan Plane (adapted from Bonnie Dorr) 1 Data Structures and Arrays c Data structures : mechanisms for storing data in a structured way c We have seen simple data structures implemented as classes: c Rational.java c Rational number data stored as numerator / denominator pair c Arrays are a very useful data structure provided by Java and other programming languages c Array: sequence of variables of the same type c homogeneous data structure c size (quantity) fixed when space is allocated c ordered c Individual elements of sequence can be referenced/updated/etc. c Arrays are objects (hence allocated on heap) with a reference on the stack c Like other objects, “instance variables” of array = cells in array are assigned default values (0 / null / etc.) when array created

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 CMSC 131 Fall 2007 Jan Plane (adapted from Bonnie Dorr) 2 Array Indexing c Java provides a special syntax for uniformly accessing cells in an array c Declaration of a: int[] a; c Allocation of space for array named a: a = new int[5]; c This creates five int variables “named”:: a[0],a[1],a[2],a[3],a[4] c To modify contents of cell #2 to 6 and cell #1 to 74: a[2] = 6; a[1] = 74; c To use the contents of cell #2 and cell #1 : System.out.println(“value = “ + (a[1]-a[2])); c This access mechanism to the individual elements is called array indexing c In Java / C / C++, array cells are indexed beginning at 0 and going up to n-1 (n is number of cells) c Beware: start at 0! and end at one less than the size!! CMSC 131 Fall 2007 Jan Plane (adapted from Bonnie Dorr) 3 Square Brackets: [ ] and length c Three uses in Java: c Array variable declaration int[] a; c Array object creation new int[10]; c Array indexing a[0] c array also has a.length holds the amount of space currently allocated for that array
3 CMSC 131 Fall 2007 Jan Plane (adapted from Bonnie Dorr) 4 Alternate Declaration Syntax c To maintain consistency with C / C++, following declaration of array variables also possible

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 11

12ArraysIntroLarge - Lecture Set#12 Arrays This lecture set...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online