CODEWITHSUNDEEP
javabigintegerbit-shiftordinal
cbm64
cbm64

Reputation: 1119

Java BigInteger and the Shift operator

I have the enum;

enum testMe {
    one,
    two,
    three;

    long longValue() {
        return 1<<ordinal();
    }
}

for (testMe myLoop = testMe.values()) {
    System.out.println(value.longValue() + ":" + myLoop);
}

Looping through the enum gives me exactly what I expect for the shift on the ordinal of the values in the enum. However, I need to qualify on an parameter I pass in a long;

Long myLong = 3;
for (testMe myLoop = testMe.values()) {
    if ((myLong & value.longValue()) != 0) {
        System.out.println(value.longValue() + ":" + myLoop);
    }
}

In this case only the One and Two will be printed. However, this method will only work to 32 values in the enum. Does anyone have any ideas how I could use the BigInteger???

    BigInteger longValue() {
        BigInteger one = BigInteger.valueOf(1);
        return one.shiftLeft(ordinal());

Thanks C

Upvotes: 0

Views: 276

Answers (2)

laune
laune

Reputation: 31290

  BigInteger b =BigInteger.ZERO;
  b = b.setBit( ordinal() );

You may also use BigInteger.and(BigInteger x).

enum OneTwo {
  one,
  two,
  three;

  BigInteger biValue() {
    BigInteger bi = BigInteger.ZERO;
    return bi.setBit(ordinal());
  }
  BigInteger biValue( BigInteger filter ) {
    BigInteger bi = BigInteger.ZERO;
    return bi.setBit(ordinal()).and(filter);
  }
}

And a test:

BigInteger three = BigInteger.valueOf(3L);
for (OneTwo ot: OneTwo.values()) {
    System.out.println( ot.biValue() + ":" + ot);
    System.out.println( ot.biValue(three) + ":" + ot);
}

No problem with printing.

Or compare to zero

if( BigInteger.ZERO.equals( bi.setBit(ordinal()).and(filter) ) ){
    // no bits in filter are set
}

Upvotes: 2

Joop Eggen
Joop Eggen

Reputation: 109547

Use EnumSet.

EnumSet<TestMe> set = new EnumSet<>(TestMe.class);

An EnumSet has the bit properties you desire, though unfortunately does not exhibit them as long[] or such. Otherwise use a BitSet.

Upvotes: 2

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