Comparable

Comparable is used to define natural ordering for user-defined types.

To do that, the class should implement the Comparable interface and define its compareTo() method.

Definition

public interface Comparable<T> {
    int compareTo(T o);
}

Implementation

compareTo() has context of two objects. One, which is being used to invoke it and the other, which it takes as an input. It then compares these two objects (the part which is to be implemented) and returns and integer indicating the order.

• Negative: current object is less than the other object.
• Zero: current object is equal to the other object.
• Positive: current object is greater than the other object.

compareTo(T o){
 if(this < o) return -1;
 
 if(this == o) return 0;

 if(this > o) return 1;
}

Usage

If a class implements this, you can use the compareTo() method to compare its two objects.

switch(obj1.compareTo(obj2)){
    case -1: // obj1 <  obj2
    case 0:  // obj1 == obj2
    case 1:  // obj1 >  obj2
}

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Backlinks

• Collection Framework (cs)
• Wrapper Classes (cs)
• String Comparison (cs)
• Comparator (cs)