Versions

[{“Name”:“Java SE 1.2”,“GroupName”:null},{“Name”:“Java SE 1.3”,“GroupName”:null},{“Name”:“Java SE 1.4”,“GroupName”:null},{“Name”:“Java SE 5”,“GroupName”:null},{“Name”:“Java SE 6”,“GroupName”:null},{“Name”:“Java SE 7”,“GroupName”:null},{“Name”:“Java SE 8”,“GroupName”:null},{“Name”:“Java SE 9 (Early Access)”,“GroupName”:null}]

Syntax

Remarks

When implementing a compareTo(..) method which depends upon a double, do not do the following:

public int comareTo(MyClass other) {
    return (int)(doubleField - other.doubleField); //THIS IS BAD
}

The truncation caused by the (int) cast will cause the method to sometimes incorrectly return 0 instead of a positive or negative number, and can thus lead to comparison and sorting bugs.

Instead, the simplest correct implementation is to use Double.compare, as such:

public int comareTo(MyClass other) {
    return Double.compare(doubleField,other.doubleField); //THIS IS GOOD
}

A non-generic version of Comparable<T>, simply Comparable, has existed since Java 1.2. Other than for interfacing with legacy code, it’s always better to implement the generic version Comparable<T>, as it doesn’t require casting upon comparison.


It is very standard for a class to be comparable to itself, as in:

public class A implements Comparable<A>

While it is possible to break from this paradigm, be cautious when doing so.