go to previous page   go to home page   go to next page

Answer:

gradeTable[ 0 ][ 0 ] 99
gradeTable[ 1 ][ 1 ] 91
gradeTable[ 3 ][ 4 ] 93
gradeTable[ 5 ][ 2 ] 92

2D Arrays in Java

StudentWeek
01234
0 99 42 74 83 100
1 90 91 72 88 95
2 88 61 74 89 96
3 61 89 82 98 93
4 93 73 75 78 99
5 50 65 92 87 94
6 43 98 78 56 99
gradeTable

In Java, a table may be implemented as a 2D array. Each cell of the array is a variable that can hold a value and works like any variable. As with one dimensional arrays, every cell in a 2D array is of the same type. The type can be a primitive type or an object reference type.

Important: Each cell of the array is specified with a row and column number, in that order.

Say that gradeTable is a 2D array of int, and that (conceptually, at least) it looks like the table to the right. Then,

gradeTable[ 0 ][ 1 ]     // holds 42
gradeTable[ 3 ][ 4 ]     // holds 93
gradeTable[ 6 ][ 2 ]     // holds 78

The subscripted variables are used in assignment statements and arithmetic expressions just like any variable:

gradeTable[ 0 ][ 1 ] = 33 ;   // puts a 33 into row 0 column 1. 
gradeTable[ 3 ][ 4 ]++ ;      // increments the value at row 3 column 4. 
int value = (gradeTable[ 6 ][ 2 ] + 2) / 2 ;  // puts 40 into value 

QUESTION 3:

Write a Java statement that puts a zero into row 5 column 3.