Java 6 Illuminated: An Active Learning Approach, 2nd Edition



Do not use the equality

operators to compare

object data;instead,use

the equals method.

COMMON ERROR

TRAP

5.9 Comparing Objects 247

Figure 5.19

Output from Example

5.11

d1 and d2 are not equal

d1 and d3 are equal

d1 data and d2 data are equal

d1 data and d4 data are not equal

Lines 10 and 11 instantiate two SimpleDate objects with the same data. Line

14 sets the d3 object reference to point to the d1 object. Line 17 instantiates

the d4 object with different data.

In line 20, when we compare d1 and d2 using the equality operator, the

result is false, because the object references d1 and d2 point to two different

objects. However, when we compare d1 and d3 (line ...