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Chapter overview

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Chapter overview

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  1. Chapter overview • This chapter focuses on • Array declaration and use • Bounds checking and capacity • Arrays storing object references • Variable length parameter lists • Multidimensional arrays • The ArrayList class

  2. one dimension two dimensions Two-dimensional arrays • A one-dimensional array stores a list of element • A two dimensional array • Can be thought of as a table of elements • With rows and columns

  3. Two dimensional arrays: declaration • To be precise, in JAVA • A two-dimensional array is an array of arrays • A two-dimensional array • is declared by specifying the size of each dimension • An array element • is referenced using two index values • The array stored in one row • Can be specified using one index int[][] scores = new int[12][50]; value = scores[3][6]

  4. Two-dimensional arrays: example • See TwoDArray.java • See SodaSurvey.java

  5. Chapter overview • This chapter focuses on • Array declaration and use • Bounds checking and capacity • Arrays storing object references • Variable length parameter lists • Multidimensional arrays • The ArrayList class

  6. The ArrayList class • The ArrayList class • is part of java.util • Can store a list of values • and reference each one using a numeric index • Dynamically grows and shrinks as needed • Adjusting its capacity as necessary • However, you cannot use the brackets syntax • With an ArrayList object

  7. ArrayList elements • ArrayList • is not declared to store a particular type • any type of object can be added to an ArrayList • stores references to different types of objects • If a primitive value must be stored in an ArrayList • Use the appropriate wrapper class

  8. Arraylist: inserting and removing elements • Elements in an ArrayList • Can be inserted or removed • with a single method invocation • When an element is inserted • Other elements move aside to make room • When an element is removed • The list collapses to close the gap • The indexes of elements adjust accordingly

  9. Specifying an ArrayList element type • See Beatles.java • we can also define • An ArrayList object to accept a particular object type • The following declaration creates an ArrayList object • that only stores Family objects ArrayList<Family> reunion = new ArrayList<Family>

  10. Methods defined in ArrayList • boolean add(Object obj) • Inserts the specified object to the end of the list • object remove(int index) • Removes the element at specified index in the list • void add(int index, Object obj) • Inserts the specified object into list at specified index • int indexOf(Object obj) • Returns the index of 1st occurrence of the specified object