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javafloating-pointbigdecimal

Float and BigDecimal precision difference

public static void main(String[] args) {
    // TODO Auto-generated method stub
    BigDecimal foo,foo1;
    foo=BigDecimal.valueOf(3.1);
    foo1=BigDecimal.valueOf(3.1f);

    System.out.println(foo);
    System.out.println(foo1);

}

RESULT:
3.1
3.0999999046325684

Why they are different result? I am using JDK1.7.0_03

Solution

  • 3.1 defines a double while 3.1f defines a float. What you see is the problem the float has of representing that value (float uses "only" 32-bits and double 64-bits).

    If you want to define a 3.1 exactly using BigDecimal use the String constructor:

    BigDecimal foo = new BigDecimal("3.1");
System.out.println(foo);

    Output:

    3.1