Validate if a String contains only numbers : Character Data Type « Data Type « Java Tutorial

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Java Tutorial » Data Type » Character Data Type

2. 7. 10. Validate if a String contains only numbers


public class Main {

  public static boolean containsOnlyNumbers(String str) {

    for (int i = 0; i < str.length(); i++) {

      if (!Character.isDigit(str.charAt(i)))

        return false;

    }

    return true;

  }



  public static void main(String[] args) {

    System.out.println(containsOnlyNumbers("123456"));

    System.out.println(containsOnlyNumbers("123abc456"));

  }

}

/*

true

false

*/

2. 7. Character Data Type
	2. 7. 1.	Java char: char is 16 bit type and used to represent Unicode characters. Range of char is 0 to 65,536.
	2. 7. 2.	Escape Sequence Characters
	2. 7. 3.	Storing Characters
	2. 7. 4.	Assign int value to char variable
	2. 7. 5.	char variables behave like integers
	2. 7. 6.	Display printable Characters
	2. 7. 7.	Character: is Upper Case
	2. 7. 8.	Character: is Lower Case
	2. 7. 9.	isDigit(): true if the argument is a digit (0 to 9), and false otherwise.
	2. 7. 10.	Validate if a String contains only numbers
	2. 7. 11.	isLetter(): true if the argument is a letter, and false otherwise.
	2. 7. 12.	Count letters in a String
	2. 7. 13.	isLetterOrDigit(): true if the argument is a letter or a digit, and false otherwise.
	2. 7. 14.	is White space
	2. 7. 15.	Is character a digit, letter, white space, lower case or upper case character
	2. 7. 16.	Convert character to digit with Character.digit
	2. 7. 17.	Demonstrate several Is... methods.
	2. 7. 18.	Convert from ASCII code to String
	2. 7. 19.	Convert from integer to ASCII code (byte)
	2. 7. 20.	To extract Ascii codes from a String
	2. 7. 21.	Copy char array to string
	2. 7. 22.	Store unicode in a char variable
	2. 7. 23.	Determining a Character's Unicode Block
	2. 7. 24.	Plus one to char variable
	2. 7. 25.	Convert string to char array
	2. 7. 26.	Compare Two Java char Arrays
	2. 7. 27.	Max and Min values of datatype char
	2. 7. 28.	Determining If a String Is a Legal Java Identifier
	2. 7. 29.	compare two objects of Character
	2. 7. 30.	ASCII character handling functions
	2. 7. 31.	Checks if the string contains only ASCII printable characters.
	2. 7. 32.	Checks whether the character is ASCII 7 bit alphabetic lower case.
	2. 7. 33.	Checks whether the character is ASCII 7 bit alphabetic upper case.
	2. 7. 34.	Checks whether the character is ASCII 7 bit alphabetic.
	2. 7. 35.	Checks whether the character is ASCII 7 bit control.
	2. 7. 36.	Checks whether the character is ASCII 7 bit numeric and character.
	2. 7. 37.	Checks whether the character is ASCII 7 bit numeric.
	2. 7. 38.	Checks whether the character is ASCII 7 bit printable.
	2. 7. 39.	Checks whether the character is ASCII 7 bit.
	2. 7. 40.	Determines if the specified string is permissible as a Java identifier.
	2. 7. 41.	Thansform an array of ASCII bytes to a string. the byte array should contains only values in [0, 127].
	2. 7. 42.	Utility methods for ASCII character checking.

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