Java How to Program Fourth Edition - DCC

316 Arrays Chapter 7
Let us examine array c in Figure 7.1 more closely. The name of the array is c. Every
array in Java knows its own length and maintains this information in a variable called
length. The expression c.length accesses array c’s length variable to determine
the length of the array. The array’s 12 elements are referred to as c[ 0 ], c[ 1 ], c[ 2 ],
…, c[ 11 ]. The value of c[0] is -45, the value of c[ 1 ] is 6, the value of c[ 2 ] is
0, the value of c[ 7 ] is 62 and the value of c[ 11 ] is 78. To calculate the sum of the
values contained in the first three elements of array c and store the result in variable sum,
we would write
sum = c[ 0 ] + c[ 1 ] + c[ 2 ];
To divide the value of the seventh element of array c by 2 and assign the result to the variable
x, we would write
x = c[ 6 ] / 2;
Common Programming Error 7.1
It is important to note the difference between the “seventh element of the array” and “array
element seven.” Because array subscripts begin at 0, the “seventh element of the array” has
a subscript of 6, while “array element seven” has a subscript of 7 and is actually the eighth
element of the array. This confusion is a source of “off-by-one” errors. 7.1
The brackets used to enclose the subscript of an array are one of Java’s many operators.
Brackets are in the highest level of precedence in Java. The chart in Fig. 7.2 shows the precedence
and associativity of the operators introduced so far. They are shown top to bottom
in decreasing order of precedence with their associativity and type. See Appendix C for the
complete operator precedence chart.
Operators Associativity Type
() [] . left to right highest
++ -- right to left unary postfix
++ -- + - ! (type) right to left unary
* / % left to right multiplicative
+ - left to right additive
< >= left to right relational
== != left to right equality
& left to right boolean logical AND
^ left to right boolean logical exclusive OR
| left to right boolean logical inclusive OR
&& left to right logical AND
|| left to right logical OR
?: right to left conditional
= += -= *= /= %= right to left assignment
Fig. Fig. 7.2 7.2 Precedence and associativity of the operators discussed so far.
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