How to Convert a String to an Array in Java

Java makes it easy to convert a string to an array by providing the built-in .split() method on the String object.

The challenge

Write a function to split a string and convert it into an array of words. For example:

"Robin Singh" ==> ["Robin", "Singh"]

"I love arrays they are my favorite" ==> ["I", "love", "arrays", "they", "are", "my", "favorite"]

The solution in Java code

This is a really simple one, you just split the string with the space character:

public class Solution {

    public static String[] stringToArray(String s) {
      return s.split(" ");
    }

}

However, if you prefer not to use the space character, you can opt for using \\s+ instead:

public class Solution {

    public static String[] stringToArray(String s) {
      return s.split("\\s+");
    }

}

Test cases to validate our Java solution

import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {
    @Test
    public void basicTests() {
        assertArrayEquals(new String[]{"Robin", "Singh"}, Solution.stringToArray("Robin Singh"));
        assertArrayEquals(new String[]{"I", "love", "arrays", "they", "are", "my", "favorite"}, Solution.stringToArray("I love arrays they are my favorite"));
    }
}

Building additional test cases

import org.junit.Test;
import static org.junit.Assert.assertArrayEquals;
import org.junit.runners.JUnit4;

public class SolutionTest {
    @Test
    public void basicTests() {
        assertArrayEquals(new String[]{"Robin", "Singh"}, Solution.stringToArray("Robin Singh"));
        assertArrayEquals(new String[]{"I", "love", "arrays", "they", "are", "my", "favorite"}, Solution.stringToArray("I love arrays they are my favorite"));
    }
    
    @Test
    public void randomTests() {
      for(int i = 0; i < 200; i++){
        String testString = makeString(0,30);
        assertArrayEquals(randomTest(testString), Solution.stringToArray(testString));
      }
    }
    
    private String makeString(int min, int max) {
      StringBuilder sb = new StringBuilder();
      int length = (int)Math.ceil((Math.random() * max) + min);
  
      for (int i = 0; i < length; i++) {
          sb.append(makeWord(min, max));
          if (i < length-1) sb.append(" ");
      }
      return sb.toString();
    }
    
    private String makeWord(int min, int max) {
      StringBuilder sb = new StringBuilder();
      String possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
      int length = (int)Math.ceil((Math.random() * max) + min);
    
      for(int i = 0; i < length; i++) {
          sb.append(possible.charAt((int)Math.floor(Math.random() * possible.length())));
      }
    
      return sb.toString();
    }
    
    private String[] randomTest(String s){
      return s.split(" ");
    }

}
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