Java Double.compareTo() Method

The Double.compareTo() method is a built-in method in Java of java.lang package. This method is used to compare two Double objects numerically. This method returns 0 if this object is equal to the argument object, it returns less than 0 if this object is numerically less than the argument object, and a value greater than 0 if this object is numerically greater than the argument object. 

In this article, we are going to learn about the Double.compareTo() method in Java with examples.

Syntax of Double.compareTo() Method

public int compareTo(Double anotherDouble)

Parameter: obj: The object that is to be compared to. 

Return Values: The function can return three values:

• equal to 0: Object is equal to the argument object.
• less than 0: Object is less than the argument object.
• greater than 0: Object is greater than the argument object.

Note: This method only accepts a Double object as an argument. If we pass anything else or no argument at all, it will result in a compile-time error.

Examples of Java Double.compareTo() Method

Example 1: In this example, we are going to compare two different Double objects.

// Java program to demonstrate Double.compareTo() method
import java.lang.Double;

public class Geeks {
    
    public static void main(String[] args) {
        
        Double obj1 = new Double(124);
        Double obj2 = new Double(167);

        int compareValue = obj1.compareTo(obj2);

        if (compareValue == 0)
            System.out.println("obj1 and obj2 are equal");
        else if (compareValue < 0)
            System.out.println("obj1 is less than obj2");
        else
            System.out.println("obj1 is greater than obj2");
    }
}

obj1 is less than obj2

Example 2: In this example, we are going to pass no argument and see what happens.

// No argument passed
import java.lang.Double;

public class Geeks {
    
    public static void main(String[] args) {
        Double obj1 = new Double(124);

        // This will result in a compile-time error
        int result = obj1.compareTo(); 
    }
}

Output:

error: method compareTo in class Double cannot be applied to given types;
        int result = obj1.compareTo(); 
                         ^
  required: Double
  found: no arguments
  reason: actual and formal argument lists differ in length

Example 3: In this example, we are going to pass a non-Double object.

// Passing incompatible type
import java.lang.Double;

public class Geeks {
    
    public static void main(String[] args) {
        Double obj1 = new Double(124);

        // This will also result in a compile-time error
        int result = obj1.compareTo("gfg"); 
    }
}

Output:

error: incompatible types: String cannot be converted to Double

Important Points:

• Always make sure the object passed to compareTo() method is of type Double.
• Do not use raw objects like Object in compareTo() for wrapper classes, always prefer using the typed version.
• For comparing primitive double values directly, consider using Double.compare(double d1, double d2).