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Java Understanding Math.getExponent(Double)

Double dble = new Double("2.2737367544323201e-13");
int exponent = Math.getExponent(dble);

I have the above code and exponent has value of '-43'. I'm not sure how the exponent is '-43', when the passed double value contains '-13'. Could someone shed some light into this API?

Solution

  • Math.getExponent() returns the exponent of the binary representation of the number. In your example -13 is the exponent of the decimal representation, and -43 the exponent of the binary representation.

    For example,

    System.out.println (Math.getExponent (1024));

    prints

    10

    since

    1024 = 2 ^ 10

    so the exponent is 10.

    System.out.println (Math.getExponent (1.0/8192));

    will print

    -13

    since

    1.0/8192 = 2 ^ (-13)