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Fix the equals and hashCode methods so that sets work as expected

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This commit is contained in:
DjBushido 2014-01-22 15:17:45 -05:00
parent 57dfd938fa
commit 8b893cd06a
2 changed files with 26 additions and 5 deletions
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6
HW1/src/edu/uncc/itcs4180/PartTwo/PartTwo.java
View File

@ -41,10 +41,10 @@ public class PartTwo {
reader.close(); reader.close();
} catch (FileNotFoundException e) { } catch (FileNotFoundException e) {
System.out.println("Could not open file: " + filename); System.err.println("Could not open file: " + filename);
return; return;
} catch (IOException e) { } catch (IOException e) {
System.out.println("Error reading the CSV file."); System.err.println("Error reading the CSV file.");
return; return;
} }
@ -61,7 +61,7 @@ public class PartTwo {
writer.close(); writer.close();
} catch (IOException e) { } catch (IOException e) {
System.err.println("Error writing unique vehicles to CSV"); System.err.println("Error writing unique vehicles to CSV.\n" + e.getMessage());
// Don't return here, we can still complete the rest of the program // Don't return here, we can still complete the rest of the program
} }

25
HW1/src/edu/uncc/itcs4180/PartTwo/Vehicle.java
View File

@ -64,8 +64,8 @@ public class Vehicle {
} }
public String toCSV() { public String toCSV() {
return this.modelYear + this.manufacturerName + this.modelName + return this.modelYear + "," + this.manufacturerName + "," + this.modelName + "," +
this.horsePower + this.noCylinders + this.noGears; this.horsePower + "," + this.noCylinders + "," + this.noGears;
} }
public String toString() { public String toString() {
@ -73,4 +73,25 @@ public class Vehicle {
" Model Name: " + this.modelName + " Horsepower: " + this.horsePower + " Model Name: " + this.modelName + " Horsepower: " + this.horsePower +
" No. Cylinders: " + this.noCylinders + " No. Gears: " + this.noGears; " No. Cylinders: " + this.noCylinders + " No. Gears: " + this.noGears;
} }
// Need to implement both equals() and hashCode() for guaranteeing unique Sets
// http://stackoverflow.com/questions/16238182/hashset-contains-duplicate-entries
// Also:
// http://www.coderanch.com/t/572755/java-programmer-SCJP/certification/HashSet-adding-duplicates-hashcode-obects
@Override
public boolean equals(Object _v2) {
Vehicle v2 = (Vehicle) _v2;
return ((this.modelYear == v2.modelYear) &&
(this.manufacturerName.equals(v2.manufacturerName)) &&
(this.modelName.equals(v2.modelName)) &&
(this.horsePower == v2.horsePower) &&
(this.noCylinders == v2.noCylinders) &&
(this.noGears == v2.noGears));
}
@Override
public int hashCode() {
return this.modelYear + this.manufacturerName.hashCode() + this.modelName.hashCode() +
this.horsePower + this.noCylinders + this.noGears;
}
} }