Programming and Problem Solving with Java

10.8 Testing and Debugging | 511

whose components are arrays, arrays whose components are objects, arrays whose com-

ponents are strings, and so forth. When we use arrays of objects, confusion can arise about

precisely where to place the operators for array element selection ([]) and class field se-

lection (.).

To summarize the correct placement of these operators, let’s use a StudentRecclass

where the data fields are defined as follows:

classStudentRec

{

String stuName; // Student's name

float gpa; // Student's grade point average

int[] examScores = new int[4]; // There are four exams

char courseGrade; // A, B, C, D, or F

...

}

If we declare a variable of type StudentRecand an array of type StudentRec

StudentRec student = newStudentRec();

StudentRec[] members = newStudentRec[ 100 ];

the following chart shows how to access the fields of student. Recall that the dot opera-

tor is a binary (two-operand) operator; its left operand is a class variable or class name,

and its right operand is a field. The []operator is a unary (one-operand) operator; it comes

immediately after an expression denoting an array:

Expression Item Denoted Meaning

student

student.stuName

student.gpa

student.examScores

student.examScores[ 0 ]

student.examScores[ 4 ]

student.courseGrade

members[ 0 ]

members[ 0 ].stuName

members[ 0 ].gpa

members[ 0 ].examScores

members[ 0 ].examScores[ 1 ]

A StudentRecobject

A string

A real number

An array of int

An integer

Crash!! Index out of range

A character

A StudentRecobject

A string

A real number

An array of int

An integer

A single student

A name

A GPA

The first exam score

The first student

The name of the first student

The GPA of the first student

The exam scores for the first

student

The second score for the first

student