Vertically placing the words in a string

Please let me know a better approach to solve below problem:

Problem: Vertically arrange the words in a string and print on console.

Sample Input:

Hello Jack

Output:

H J
e a
L c
L k
o

My solution:

public static void toVerticalWords(String str){

        //split the words by whitespace
        String[] strArr = str.split("\\s");
        int maxWordLen = 0;

        //get the longest word length
        for(String strTemp : strArr) {
            if(strTemp.length() > maxWordLen)
                maxWordLen = strTemp.length();
        }

        //make a matrix of the words with each character in an array block
        char[][] charArr = new char[strArr.length][maxWordLen];
        for(int i=0; i<strArr.length; i++) {
            int j=0;
            for(char ch : strArr[i].toCharArray()){
                charArr[i][j] = ch;
                j++;
            }
        }

        //print the vertical word pattern, or transpose of above matrix (2D array)
        for(int j=0; j<maxWordLen; j++) {
            for(int i=0; i<strArr.length; i++) {
                if (i!=0)
                    System.out.print(" ");
                System.out.print(charArr[i][j]);
            }

            System.out.println();
        }
    }

I assume you are only trying to work with ASCII characters, but I would like to point out a few Unicode-related failure modes, which can be exhibited by the following code:

String[] funkyStrings = {
    "foo bar",
    "foo ba\u0308r",
    "\ud835\udcbb\u2134\u2134 \ud835\udcb7\ud835\udcb6\ud835\udcc7"
};
for (String str : funkyStrings) {
    System.out.println(str);
    toVerticalWords(str);
}

The first string produces ordinary output:

foo bar
f b
o a
o r

The second string contains a grapheme cluster that is made up from multiple code points – the a and an accent ̈ which together create the glyph ä (← that's the precomposed form showing how it should look, as not all fonts handle combined characters correctly)

foo bär
f b
o a
o ̈
 r

The third string uses mathematical glyphs which have code points beyond U+FFFF. Because Java is slightly Unicode-retarded and can't deal with such high code points properly, its chars are actually UTF-16 code units (16 bit wide, far to small for what we are dealing with here). Therefore, higher code points have to be specified as a pair of surrogate halves. The encoding for U+1D4BB is d835 dcbb in UTF-16BE. This now produces the following output:

ℴℴ 
? ?
? ?
ℴ ?
ℴ ?
 ?
 ?

Only the ℴ is displayed correctly, because it has a lower code point of U+2134. For the other characters, the surrogate halves are separated from each other, leading to invalid characters.

Not shown here: how fullwidth and halfwidth charaters can mess up your vertical layout.

The moral of the story: code points, UTF-16 code units, characters and glyphs are different things. Dealing with them correctly is excessively difficult, and I don't know about any suitable tools. If you are not prepared to deal correctly with any input you may encounter, then check that the input conforms to a subset you are comfortable with.

for (char c : str) {
    if (c > 0x7F) {
        throw new IllegalArgumentException("The input string may only contain ASCII code points");
    }
}

StackExchange Code Review Q#46624, answer score: 11