# Java Guava | LongMath log10(long x, RoundingMode mode) method with Examples

• Last Updated : 29 Jan, 2019

The method log10(long x, RoundingMode mode) of Guava’s LongMath Class accepts two parameters and calculates the base-10 logarithmic value of the first parameter rounded according to the rounding mode specified by the second parameter.

Syntax:

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```public static int log10(long x, RoundingMode mode)
```

Parameters: The method takes 2 parameters:

• x is the long value to be found log of.
• mode is the specified rounding mode.

Return Value: This method returns Base-10 logarithm of x, rounded according to the specified rounding mode.

Exceptions: This method throws following parameters:

• IllegalArgumentException: if the value x is 0 or a negative value.
• ArithmeticException: if mode is RoundingMode.UNNECESSARY and x is not a power of ten.

#### Enum RoundingMode

Enum ConstantDescription
CEILINGRounding mode to round towards positive infinity.
DOWNRounding mode to round towards zero.
FLOORRounding mode to round towards negative infinity.
HALF_DOWNRounding mode to round towards “nearest neighbor” unless both neighbors are equidistant, in which case round down.
HALF_EVENRounding mode to round towards the “nearest neighbor” unless both neighbors are equidistant, in which case, round towards the even neighbor.
HALF_UPRounding mode to round towards “nearest neighbor” unless both neighbors are equidistant, in which case round up.
UNNECESSARYRounding mode to assert that the requested operation has an exact result, hence no rounding is necessary.
UPRounding mode to round away from zero.

Below given are some examples to understand the implementation in a better way:

Example 1:

 `// Java code to show implementation of``// log10(long x, RoundingMode mode) method``// of Guava's LongMath class`` ` `import` `java.math.RoundingMode;``import` `com.google.common.math.LongMath;`` ` `class` `GFG {`` ` `    ``// Driver code``    ``public` `static` `void` `main(String args[])``    ``{``        ``long` `a1 = ``10000``;`` ` `        ``// Using log10(long x, RoundingMode mode)``        ``// method of Guava's LongMath class``        ``// The RoundingMode HALF_EVEN rounds towards``        ``// the "nearest neighbor" unless both neighbors``        ``// are equidistant, in which case, round towards``        ``// the even neighbor.``        ``System.out.println(``            ``LongMath.log10(``                ``a1,``                ``RoundingMode.HALF_EVEN));`` ` `        ``long` `a2 = ``15``;`` ` `        ``// Using log10(long x, RoundingMode mode)``        ``// method of Guava's LongMath class``        ``// The RoundingMode HALF_DOWN rounds towards``        ``// "nearest neighbor" unless both neighbors``        ``// are equidistant, in which case round down.``        ``System.out.println(``            ``LongMath.log10(a2,``                           ``RoundingMode.HALF_DOWN));``    ``}``}`

Output :

```4
1
```

Example 2 :

 `// Java code to show implementation of``// log10(long x, RoundingMode mode) method``// of Guava's LongMath class`` ` `import` `java.math.RoundingMode;``import` `com.google.common.math.LongMath;`` ` `class` `GFG {`` ` `    ``static` `int` `findlog10(``long` `x, RoundingMode mode)``    ``{``        ``try` `{``            ``// Using log10(long x, RoundingMode mode)``            ``// method of Guava's LongMath class``            ``// The RoundingMode HALF_EVEN rounds towards``            ``// the "nearest neighbor" unless both neighbors``            ``// are equidistant, in which case, round towards``            ``// the even neighbor.``            ``// This should throw "IllegalArgumentException"``            ``// as x <= 0``            ``int` `ans = LongMath.log10(x, mode);`` ` `            ``// Return the answer``            ``return` `ans;``        ``}``        ``catch` `(Exception e) {``            ``System.out.println(e);``            ``return` `-``1``;``        ``}``    ``}`` ` `    ``// Driver code``    ``public` `static` `void` `main(String args[])``    ``{``        ``long` `x = -``122``;`` ` `        ``try` `{`` ` `            ``// Function calling``            ``findlog10(x, RoundingMode.HALF_EVEN);``        ``}``        ``catch` `(Exception e) {``            ``System.out.println(e);``        ``}``    ``}``}`

Output :

```java.lang.IllegalArgumentException: x (-122) must be > 0
```

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