Java: Sort a String array in a numeric way

I have a String array that contains the following entries:

Array[0]开发者_开发技巧 = "70% Marc"
Array[1] = "50% Marc"
Array[2] = "100% Marc"
Array[3] = "20% Marc"

And I would like to sort this array descending. When I use Arrays.sort(Array) then it does sort it descending but the 100% Marc is at the bottom (because it only looks at the first character to sort it). I want it to be sorted like this:

"100% Marc"
"70% Marc"
"50% Marc"
"20% Marc"

How can I do that?

Write your own CustomStringComparator and use it with the sort method.

public class CustomStringComparator implements Comparator<String>{

    @Override
    public int compare(String str1, String str2) {

       // extract numeric portion out of the string and convert them to int
       // and compare them, roughly something like this

       int num1 = Integer.parseInt(str1.substring(0, str1.indexOf("%") - 1));
       int num2 = Integer.parseInt(str2.substring(0, str2.indexOf("%") - 1));

       return num1 - num2;

    }
}

You have to use a custom Comparator. Basically in your method compare() you will write the logic to order two Strings.

You will need a custom comparator:

import java.util.Comparator;

public class CustomComparator implements Comparator<String>{

    @Override
    public int compare(String firstString, String secondString) {
        int number1 = Integer.parseInt(firstString.substring(0, firstString.indexOf('%') - 1);
        int number2 = Integer.parseInt(secondString.substring(0, secondString.indexOf('%') - 1);
        return number1.compareTo(number2);
    }
}

Use this comparator with something like this:

List<String> entries = new ArrayList<String>();
entries.add("70% Marc");
entries.add("50% Marc");
entries.add("100% Marc");
entries.add("20% Marc");

CustomComparator comparator = new CustomComparator();
Collections.sort(entries, comparator);

It's not looking at the first character, it's sorting based on a string value as that's what you have in your array.

I would suggest storing two fields,

Array[0,0] = 50; Array[0,1] = "Marc"

And then sorting based on the numeric field, if that's the behaviour you're after.

You'd need to implement a custom Comparator<String> that handles the comparison by removing the percent sign:

public int compare(String str1, String str2) {
    Integer number1 = Integer.parseInt(str1.substring(0, str1.length - 1));
    Integer number2 = Integer.parseInt(str1.substring(0, str2.length - 1));
    return number1.compareTo(number2);
    // or use primitives, and then: return (x < y) ? -1 : ((x == y) ? 0 : 1);
    // but that's harder to read
}

The comparison itself can be done by using the Integer wrapper, the code that I pasted (taken from the wrapper), or guava's Ints.compare(int1, int2)

Then use Collections.sort(array, comparator)