Java比较整数和大整数
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Java compare integer and bigInteger
提问by Progo
How do I compare an intwith a BigIntegerin Java? I specifically need the know if an intis less than a BigInteger. Here is the code I am using:
我如何将 anint与BigIntegerJava 中的a进行比较？我特别需要知道 anint是否小于 a BigInteger。这是我正在使用的代码：
private static BigInteger two = new BigInteger("2");
private static BigInteger three = new BigInteger("3");
private static BigInteger zero = new BigInteger("0");
public static BigInteger bigIntSqRootCeil(BigInteger x) throws IllegalArgumentException {
if (x.compareTo(BigInteger.ZERO) < 0) {
throw new IllegalArgumentException("Negative argument.");
}
if (x == BigInteger.ZERO || x == BigInteger.ONE) {
return x;
}
BigInteger two = BigInteger.valueOf(2L);
BigInteger y;
for (y = x.divide(two);
y.compareTo(x.divide(y)) > 0;
y = ((x.divide(y)).add(y)).divide(two));
if (x.compareTo(y.multiply(y)) == 0) {
return y;
} else {
return y.add(BigInteger.ONE);
}
}
private static boolean isPrimeBig(BigInteger n){
if (n.mod(two) == zero)
return (n.equals(two));
if (n.mod(three) == zero)
return (n.equals(three));
BigInteger m = bigIntSqRootCeil(n);
for (int i = 5; i <= m; i += 6) {
if (n.mod(BigInteger.valueOf(i)) == zero)
return false;
if(n.mod(BigInteger.valueOf(i + 2)) == zero)
return false;
};
return true;
};
Thanks.
谢谢。
采纳答案by Joe
How do I compare an int with a BigInteger in Java? I specifically need the know if an int is less than a BigInteger.
如何在 Java 中比较 int 和 BigInteger？我特别需要知道 int 是否小于 BigInteger。
Turn the intinto a BigIntegerbefore comparing:
转int成一个BigInteger比较之前：
if (BigInteger.valueOf(intValue).compareTo(bigIntegerValue) < 0) {
// intValue is less than bigIntegerValue
}
回答by Am_I_Helpful
Instead of
代替
if (x == BigInteger.ZERO || x == BigInteger.ONE) {
return x;
You should use :-
你应该使用：-
if (x.equals(BigInteger.ZERO) || x.equals(BigInteger.ONE)){
return x;
Also, you should change the Integer first to BigInteger, and then compare, as mentioned by Joein his answer:
此外，您应该先将 Integer 更改为 BigInteger，然后进行比较，如Joe他的回答中所述：
Integer a=3;
if(BigInteger.valueOf(a).compareTo(BigInteger.TEN)<0){
// your code...
}
else{
// your rest code, and so on.
}
回答by Mureinik
Just use BigInteger.compare:
只需使用BigInteger.compare：
int myInt = ...;
BigInteger myBigInt = ...;
BigInteger myIntAsABigInt = new BigInteger(String.valueOf(myInt));
if (myBigInt.compareTo(myIntAsABigInt) < 0) {
System.out.println ("myInt is bigger than myBigInt");
} else if (myBigInt.compareTo(myIntAsABigInt) > 0) {
System.out.println ("myBigInt is bigger than myInt");
} else {
System.out.println ("myBigInt is equal to myInt");
}
