Java Numeric Literals with Underscore

A new feature was introduced by JDK 7 which allows writing numeric literals using the underscore character. Numeric literals are broken to enhance the readability. This feature is used to separate a group of digits in numeric literal which can improve the readability of source code. There are some rules the programmer has to follow before using numeric literals like

1. We should not use underscore before or after an integer number.

int p = _10; // Error, this is an identifier, not a numeric literal  
int p = 10_; // Error, cannot put underscores at the end of a number  

2. We should not use underscore before or after a decimal point in a floating-point literal.

float a = 10._0f; // Error, cannot put underscores adjacent to a decimal point  
float a = 10_.0f; // Error, cannot put underscores adjacent to a decimal point  

3. We should not use prior to L or F suffix in long and float integers respectively.

long a = 10_100_00_L; // Error, cannot put underscores prior to an L suffix  
float a = 10_100_00_F; // Error, cannot put underscores prior to an F suffix  

4. We cannot use underscore in positions where a string of digits is expected.

Example

Java

// Java program to demonstrate Numeric Literals with
// Underscore

public class Example {
    public static void main(String args[])
    {
        // Underscore in integral literal
        int a = 7_7;
        System.out.println("The value of a is=" + a);

        // Underscore in floating literal
        double p = 11.239_67_45;
        System.out.println("The value of p is=" + p);

        float q = 16.45_56f;
        System.out.println("The value of q is=" + q);

        // Underscore in binary literal
        int c = 0B01_01;
        System.out.println("c = " + c);

        // Underscore in hexadecimal literal
        int d = 0x2_2;
        System.out.println("d = " + d);

        // Underscore in octal literal
        int e = 02_3;
        System.out.println("e = " + e);
    }
}

Output

The value of a is=77
The value of p is=11.2396745
The value of q is=16.4556
c = 5
d = 34
e = 19

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