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Integer toOctalString() Method in Java
• Last Updated : 06 Jul, 2018

Octal is the base-8 number system and uses the digits 0 to 7 in operation. Octal is widely used in computing on systems like the PDP-8, and IBM mainframes employed 12-bit, 24-bit or 36-bit words.
The Java.lang.Integer.toOctalString() method is a built-in function in Java that is used to return a string representation of the integer argument as an unsigned integer in base 8.

Syntax:

`public static String toOctalString(int num)`

Parameters : The method accepts a single parameter num of integer type which is requiered to be converted to a string.

Return Value: The function returns a string representation of the integer argument as an unsigned integer in base 8.

Examples:

``` Consider an integer a = 86
Octal output = 126

Consider an integer a = 186
Octal output = 272
```

Below programs illustrate the working of Integer.toOctalString() method:
Program 1: For positive integer:

 `// Java program to demonstrate working``// of Integer.toOctalString() method`` ` `import` `java.lang.*;`` ` `public` `class` `Geeks {`` ` `    ``public` `static` `void` `main(String[] args)``    ``{`` ` `        ``int` `a = ``527``;``        ``System.out.println(``"Integral Number = "` `+ a);`` ` `        ``// returns the string representation of the unsigned int value``        ``// represented by the argument in octal (base 8)``        ``System.out.println(``"Octal Number = "` `+ Integer.toOctalString(a));``    ``}``}`
Output:
```Integral Number = 527
Octal Number = 1017
```

Program 2: For Negative integer:

 `// Java program to demonstrate working``// of Integer.toOctalString() method`` ` `import` `java.lang.*;`` ` `public` `class` `Geeks {`` ` `    ``public` `static` `void` `main(String[] args)``    ``{`` ` `        ``int` `a = -``51``;``        ``System.out.println(``"Integral Number = "` `+ a);`` ` `        ``// Returns the string representation of the unsigned int value``        ``// in octal (base 8)``        ``System.out.println(``"Octal Number = "` `+ Integer.toOctalString(a));``    ``}``}`
Output:
```Integral Number = -51
Octal Number = 37777777715
```

Program 3: For decimal value or a string:
Note: Whenever a decimal number or a string is passed as an argument, it returns an error message which results incompatible types.

 `// Java program to demonstrate working``// of Integer.toOctalString() method`` ` `import` `java.lang.*;`` ` `public` `class` `Geeks {`` ` `    ``public` `static` `void` `main(String[] args)``    ``{`` ` `        ``double` `a = ``18.71``;`` ` `        ``// Returns the string representation of the unsigned int value``        ``// in octal (base 8)``        ``System.out.println(``"Octal output = "` `+ Integer.toOctalString(a));`` ` `        ``String b = ``"63"``;`` ` `        ``// Returns the string representation of the unsigned int value``        ``// in octal (base 8)``        ``System.out.println(``"Octal output = "` `+ Integer.toOctalString(a));``    ``}``}`

Output:

```prog.java:15: error: incompatible types: possible lossy conversion from double to int
System.out.println("Octal output = " + Integer.toOctalString(a));
^
prog.java:21: error: incompatible types: possible lossy conversion from double to int
System.out.println("Octal output = " + Integer.toOctalString(a));
^
Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
2 errors
```

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