CODEWITHSUNDEEP
javastringhex
Anandhu
Anandhu

Reputation: 67

check hex string contains only hex bounded values

How to check a given hex string contains only hex number. is there is any simple method or any java library for the same?i have string like "01AF" and i have to check string only contains hex range values,for that what i am doing now is take the string and then split the string and then converted it to appropriate format then make a check for that value.is there is any simple method for that?

Upvotes: 3

Views: 10665

Answers (5)

gouessej
gouessej

Reputation: 4076

You can use a switch expression:

public static boolean isHex(final String str) {
    return str != null && 
           !str.isEmpty() && 
           str.codePoints()
              .allMatch((final int codePoint) -> switch (codePoint) {
            case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                 'A', 'B', 'C', 'D', 'E', 'F', 
                 'a', 'b', 'c', 'd', 'e', 'f' -> true;
            default -> false;
    });
}

This solution is more efficient than using a regular expression and it doesn't rely on a try catch.

Upvotes: 0

Gerardo Roza
Gerardo Roza

Reputation: 3374

If anyone reached this thread trying to avoid the following exception when parsing a Mongodb ObjectId:

java.lang.IllegalArgumentException: invalid hexadecimal representation of an ObjectId: [anInvalidId]

Then note this utility method offered by the mongo-java-driver library:

ObjectId.isValid(stringId)

Related thread:

How to determine if a string can be used as a MongoDB ObjectID?

Upvotes: 0

barak manos
barak manos

Reputation: 30136

Given String str as your input string:

Option #1:

public static boolean isHex(String str)
{
    try
    {
        int val = Integer.parseInt(str,16);
    }
    catch (Exception e)
    {
        return false;
    }
    return true;
}

Option #2:

private static boolean[] hash = new boolean[Character.MAX_VALUE];
static // Runs once
{
    for (int i=0; i<hash.length; i++)
        hash[i] = false;
    for (char c : "0123456789ABCDEFabcdef".toCharArray())
        hash[c] = true;
}
public static boolean isHex(String str)
{
    for (char c : str.toCharArray())
        if (!hash[c])
            return false;
    return true;
}

Upvotes: 1

Pshemo
Pshemo

Reputation: 124225

If you want to check if string contains only 0-9, a-h or A-H you can try using 

yourString.matches("[0-9a-fA-F]+");

To optimize it you can earlier create Pattern 

Pattern p = Pattern.compile("[0-9a-fA-F]+");

and later reuse it as 

Matcher m = p.matcher(yourData);
if (m.matches())

and even reuse Matcher instance with 

m.reset(newString);
if (m.matches())

Upvotes: 3

Kakarot
Kakarot

Reputation: 4252

try
{
    String hex = "AAA"
    int value = Integer.parseInt(hex, 16);  
    System.out.println("valid hex);
 }
 catch(NumberFormatException nfe)
 {
    // not a valid hex
    System.out.println("not a valid hex);
 }

This will throw NumberFormatException if the hex string is invalid.

Refer the documentation here

Upvotes: 4

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