CODEWITHSUNDEEP
javaandroidstring
Ioan Moldovan
Ioan Moldovan

Reputation: 2412

How to compare string which contains integers in JAVA

I have some problem with comparing strings which contain integers. Something like A11 and A9 or BA230 and BA7 or 123 and 9 I know when I want to compare integers (which are string types), I need to pass into Integer and compare But this is not that case.

It also contains letters and numbers so I can't pass into Integer.

When I compare A11 and A9 using compareTo method, it says A9 is bigger. And when I compare 123 with 9 it says 9 is bigger.

Has anyone faced this issue before? Could you please help me? Thanks.

Upvotes: 0

Views: 1979

Answers (3)

Ioan Moldovan
Ioan Moldovan

Reputation: 2412

/**
 * Similar to compareTo method But compareTo doesn't return correct result for string+integer strings something like `A11` and `A9`
  */

private int newCompareTo(String comp1, String comp2) {
    // If any value has 0 length it means other value is bigger
    if (comp1.length() == 0) {
        if (comp2.length() == 0) {
            return 0;
        }
        return -1;
    } else if (comp2.length() == 0) {
        return 1;
    }
    // Check if first string is digit
    if (TextUtils.isDigitsOnly(comp1)) {
        int val1 = Integer.parseInt(comp1);
        // Check if second string is digit
        if (TextUtils.isDigitsOnly(comp2)) { // If both strings are digits then we only need to use Integer compare method
            int val2 = Integer.parseInt(comp2);
            return Integer.compare(val1, val2);
        } else { // If only first string is digit we only need to use String compareTo method
            return comp1.compareTo(comp2);
        }

    } else { // If both strings are not digits

        int minVal = Math.min(comp1.length(), comp2.length()), sameCount = 0;

        // Loop through two strings and check how many strings are same
        for (int i = 0;i < minVal;i++) {
            char leftVal = comp1.charAt(i), rightVal = comp2.charAt(i);
            if (leftVal == rightVal) {
                sameCount++;
            } else {
                break;
            }
        }
        if (sameCount == 0) {
            // If there's no same letter, then use String compareTo method
            return comp1.compareTo(comp2);
        } else {
            // slice same string from both strings
            String newStr1 = comp1.substring(sameCount), newStr2 = comp2.substring(sameCount);
            if (TextUtils.isDigitsOnly(newStr1) && TextUtils.isDigitsOnly(newStr2)) { // If both sliced strings are digits then use Integer compare method
                return Integer.compare(Integer.parseInt(newStr1), Integer.parseInt(newStr2));
            } else { // If not, use String compareTo method
                return comp1.compareTo(comp2);
            }
        }
    }
}

Upvotes: 3

winston
winston

Reputation: 37

public int compareTo(String anotherString) {
        int len1 = value.length;
        int len2 = anotherString.value.length;
        int lim = Math.min(len1, len2);
        char v1[] = value;
        char v2[] = anotherString.value;

        int k = 0;
        while (k < lim) {
            char c1 = v1[k];
            char c2 = v2[k];
            if (c1 != c2) {
                return c1 - c2;
            }
            k++;
        }
        return len1 - len2;
    }

String.compareTo is compare every character's unicode value one by one. it will return when find that two character not equal.

A11 compare to A9:

step1: 'A' compare to 'A'

step2: '1' compare to '9' . '1' unicode value is 49, '9' unicode value is 57.

So A9 is bigger.

order_by is the same as above .

order_by

Upvotes: 0

Peter Alwin
Peter Alwin

Reputation: 239

public static String extractNumber(final String str) {                

if(str == null || str.isEmpty()) return "";

StringBuilder sb = new StringBuilder();
boolean found = false;
for(char c : str.toCharArray()){
    if(Character.isDigit(c)){
        sb.append(c);
        found = true;
    } else if(found){
        // If we already found a digit before and this char is not a digit, stop looping
        break;                
    }
}

return sb.toString();
}

For input "123abc", the method above will return 123.

For "abc1000def", 1000.

For "555abc45", 555.

For "abc", will return an empty string.

// Then you can parse that to integer and then compare

Upvotes: 0

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