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StrictMath log1p() Method in Java
• Last Updated : 23 Jul, 2018

The java.lang.StrictMath.log1p() is an in-built method in Java which is used to accept a double value as argument and returns the natural logarithm of the sum of the argument and 1.

Syntax:

`public static double log1p(double x)`

Parameters: The function accepts a double value x as parameter and calculates the natural algorithm of (1+x).

Return Values: This method returns the value ln(1+x). The result of log1p(x) is almost as close as the actual result of ln(1 + x) for small values x than the floating-point evaluation of log(1.0+x).

Following cases are considered :

• The function returns positive infinity if the argument is positive infinity.
• The function returns negative infinity for negative infinty.
• The function returns NaN if the argument is NaN or less than -1.
• The function returns zero with the sign same as that of the argument if the argument is zero.

Examples:

```Input : 2018.0
Output : 7.610357618312838

Input : -4743.0
Output : NaN
```

Below programs illustrate the working of java.lang.StrictMath.log1p() function:

Program 1: In this program, finite and non-zero argument is passed.

 `// Java Program to illustrate ``// StrictMath.log1p() function `` ` `import` `java.io.*;``import` `java.lang.*;`` ` `class` `GFG {``    ``public` `static` `void` `main(String[] args)``    ``{`` ` `        ``double` `val1 = ``2018.00567``, val2 = ``99999.0``;`` ` `        ``System.out.println(``"Natural Logarithm of "` `+ ``        ``(val1 + ``1``) + ``" is "` `+ StrictMath.log1p(val1));`` ` `        ``System.out.println(``"Natural Logarithm of "` `+``        ``(val2 + ``1``) + ``" is "` `+ StrictMath.log1p(val2));``    ``}``}`
Output:
```Natural Logarithm of 2019.00567 is 7.610360426629845
Natural Logarithm of 100000.0 is 11.512925464970229
```

Program 2: In this program, infinite and negative arguments are passed.

 `// Java Program to illustrate ``// StrictMath.log1p() function `` ` `import` `java.io.*;``import` `java.lang.*;`` ` `class` `GFG {``    ``public` `static` `void` `main(String[] args)``    ``{`` ` `        ``double` `val1 = ``201800` `/ (``0.0``), val2 = -``4743.0``;`` ` `        ``System.out.println(``"Natural Logarithm of "` `+ ``        ``(val1 + ``1``) + ``" is "` `+ StrictMath.log1p(val1));`` ` `        ``System.out.println(``"Natural Logarithm of "` `+``        ``(val2 + ``1``) + ``" is "` `+ StrictMath.log1p(val2));``    ``}``}`
Output:
```Natural Logarithm of Infinity is Infinity
Natural Logarithm of -4742.0 is NaN
```

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