Java Guava BigIntegerMath sqrt()用法及代碼示例

Guava BigIntegerMath類的方法sqrt(BigInteger x，RoundingMode模式)返回x的平方根，並以指定的舍入模式進行四舍五入。

用法:

public static BigInteger sqrt(BigInteger x, RoundingMode mode)

參數：此方法采用以下參數：

x：要找到其平方根的BigInteger編號。
mode：用於計算平方根的舍入模式。

返回值：此方法返回x的平方根，並使用指定的舍入模式進行舍入。

異常：此方法引發以下異常：

IllegalArgumentException：如果x <0。
ArithmeticException：如果mode為RoundingMode.UNNECESSARY且sqrt(x)不是整數。

Enum RoundingMode

枚舉常量	描述
CEILING	舍入模式向正無窮大舍入。
DOWN	舍入模式向零舍入。
FLOOR	舍入模式向負無窮大舍入。
HALF_DOWN	除非兩個鄰居等距，否則舍入模式將朝“nearest neighbor”舍入。
HALF_EVEN	舍入模式向“nearest neighbor”舍入，除非兩個鄰居都等距，在這種情況下，向偶數鄰居舍入。
HALF_UP	除非兩個鄰居等距，否則舍入模式將朝“nearest neighbor”舍入。
UNNECESSARY	舍入模式可以斷言所請求的操作具有準確的結果，因此不需要舍入。
UP	舍入模式從零舍入。

以下示例說明了BifIntegerMath.sqrt()方法：

範例1：

// Java code to show implementation of 
// sqrt(BigInteger x, RoundingMode mode) method 
// of Guava's BigIntegerMath class 
  
import java.math.*; 
import com.google.common.math.BigIntegerMath; 
  
class GFG { 
  
    // Driver code 
    public static void main(String args[]) 
    { 
        BigInteger x1 = BigInteger.valueOf(226); 
  
        // Using sqrt(BigInteger x, RoundingMode mode) 
        // method of Guava's BigIntegerMath class 
        // The RoundingMode HALF_EVEN rounds towards 
        // the nearest neighbor unless both neighbors 
        // are equidistant, in which case, round towards 
        // the even neighbor. 
        BigInteger ans1 = BigIntegerMath 
                              .sqrt(x1, 
                                    RoundingMode.HALF_EVEN); 
  
        System.out.println("Square root of " + x1 
                           + "with HALF_EVEN rounding mode is:"
                           + ans1); 
  
        BigInteger x2 = BigInteger.valueOf(154); 
  
        // Using sqrt(BigInteger x, RoundingMode mode) 
        // method of Guava's BigIntegerMath class 
        // The RoundingMode FLOOR rounds towards 
        // negative infinity. 
        BigInteger ans2 = BigIntegerMath 
                              .sqrt(x2, 
                                    RoundingMode.FLOOR); 
  
        System.out.println("Square root of " + x2 
                           + "with FLOOR rounding mode is:"
                           + ans2); 
    } 
}

輸出：

Square root of 226with HALF_EVEN rounding mode is:15
Square root of 154with FLOOR rounding mode is:12

範例2：

// Java code to show implementation of 
// sqrt(BigInteger x, RoundingMode mode) method 
// of Guava's BigIntegerMath class 
  
import java.math.*; 
import com.google.common.math.BigIntegerMath; 
  
class GFG { 
  
    // Driver code 
    public static void main(String args[]) 
    { 
  
        try { 
            BigInteger x1 = BigInteger.valueOf(-65); 
  
            // Using sqrt(BigInteger x, RoundingMode mode) 
            // method of Guava's BigIntegerMath class 
            // The RoundingMode HALF_EVEN rounds towards 
            // the nearest neighbor unless both neighbors 
            // are equidistant, in which case, round towards 
            // the even neighbor. 
            BigInteger ans1 = BigIntegerMath 
                                  .sqrt(x1, 
                                        RoundingMode.HALF_EVEN); 
  
            // This should throw "IllegalArgumentException" 
            // as x1 < 0 
        } 
        catch (Exception e) { 
            System.out.println("Exception:" + e); 
        } 
    } 
}

輸出：

Exception:java.lang.IllegalArgumentException:x (-65) must be >= 0

參考： https://google.github.io/guava/releases/21.0/api/docs/com/google/common/math/BigIntegerMath.html#sqrt-java.math.BigInteger-java.math.RoundingMode-

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