Java BigInteger减法()方法及示例

java.math.BigInteger .subtract(BigInteger val)用于计算两个BigIntegers的算术差。该方法适用于范围远大于Java最大数据类型double范围的大数值，而不影响结果的精度，但由于BigInteger类内部使用整数数组进行处理，对BigIntegers对象的操作不如对基数的操作快。该方法对当前的BigInteger进行操作，该方法被调用，BigInteger作为参数被传递。

语法

public BigInteger subtract(BigInteger val)

参数： 该方法接受一个参数val，即要从这个BigInteger中减去的值。

返回值： 该方法返回一个BigInteger，该值为差值（this – val）。

下面的程序用来说明BigInteger的减法（）方法。

例1:

// Java program to demonstrate
// subtract() method of BigInteger
  
import java.math.BigInteger;
  
public class GFG {
    public static void main(String[] args)
    {
        // BigInteger object to store result
        BigInteger diff;
  
        // For user input
        // Use Scanner or BufferedReader
  
        // Two objects of String created
        // Holds the values to calculate the difference
        String input1
            = "56454210032311316797946498748";
        String input2
            = "34664864678464621214565587864";
  
        // Convert the string input to BigInteger
        BigInteger a
            = new BigInteger(input1);
        BigInteger b
            = new BigInteger(input2);
  
        // Using subtract() method
        diff = a.subtract(b);
  
        // Display the result in BigInteger
        System.out.println("The difference of\n"
                           + a + " \nand\n" + b + " "
                           + "\nis\n" + diff);
    }
}

输出。

The difference of
56454210032311316797946498748 
and
34664864678464621214565587864 
is
21789345353846695583380910884

例2:

// Java program to demonstrate
// subtract() method of BigInteger
  
import java.math.BigInteger;
  
public class GFG {
    public static void main(String[] args)
    {
        // BigInteger object to store result
        BigInteger diff;
  
        // For user input
        // Use Scanner or BufferedReader
  
        // Two objects of String created
        // Holds the values to calculate the difference
        String input1 = "012345678901234567"
                        + "8901234567890123"
                        + "4567890123456789"
                        + "0123456789012345"
                        + "6789012345678901"
                        + "2345678901234567"
                        + "8901234567890123"
                        + "4567890123456789"
                        + "0123456789012345"
                        + "6789012345678901"
                        + "2345678901234567"
                        + "8901234567890123"
                        + "4567890123456789"
                        + "0123456789012345"
                        + "6789012345678901"
                        + "2345678901234567"
                        + "8901234567890123"
                        + "4554324324362432"
                        + "7674637264783264"
                        + "7832678463726478"
                        + "3264736274673864"
                        + "7364732463546354"
                        + "6354632564532645"
                        + "6325463546536453"
                        + "6546325463546534"
                        + "6325465345326456"
                        + "4635463263453264"
                        + "654632498739473";
  
        String input2 = "0123456789012345"
                        + "6789012345678901"
                        + "2345678901234567"
                        + "8901234567890123"
                        + "4567890123456789"
                        + "0123456789012345"
                        + "6789012345678901"
                        + "2345678901234567"
                        + "8901234567890123"
                        + "4567890123456789"
                        + "0123456789012345"
                        + "6789012345678901"
                        + "2345678901234567"
                        + "8901234567890123"
                        + "4567890123456789"
                        + "0123456789012345"
                        + "6789012345678901"
                        + "2345873271893718"
                        + "2974897146378481"
                        + "7489127847281478"
                        + "2174871248721847"
                        + "8748327463756475"
                        + "6745781641263981"
                        + "2839721897438974"
                        + "3286574365764576"
                        + "2376914689217817"
                        + "4362473624721647"
                        + "61247612748612746";
  
        // Convert the string input to BigInteger
        BigInteger a
            = new BigInteger(input1);
        BigInteger b
            = new BigInteger(input2);
  
        // Using subtract() method
        diff = a.subtract(b);
  
        // Display the result in BigInteger
        System.out.println("The difference of\n"
                           + a + " \nand\n" + b + " "
                           + "\nis\n" + diff);
  
        // Using double to hold  the result
        double d = Double.parseDouble(diff.toString());
  
        // Display the result in double
        System.out.println("Using double, difference is "
                           + d);
    }
}

输出。

The difference of
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234554324324362432767463726478326478326784637264783264736274673864736473246354635463546325645326456325463546536453654632546354653463254653453264564635463263453264654632498739473
and
1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234587327189371829748971463784817489127847281478217487124872184787483274637564756745781641263981283972189743897432865743657645762376914689217817436247362472164761247612748612746
is
-33002865009396981507737306491010801062644213434222388597510922746801391210121282235315618654827646726197360979211111111291108913660035764552871611899208711496592980249873273
Using double, difference is -3.300286500939698E172

从上面的例子可以看出，使用BigInteger时，数据是完全精确的。

参考: https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/math/BigInteger.html#subtract(java.math.BigInteger)