Java中带有条件的多个for循环

Question

I know this is very simple question, but I just started leaning a new language. Hence need some inputs.

Problem: I had three strings with different lengths. I need to invoke the method to display one character of each string every time. If respective character is not available then I need to pass an empty char (default value)

public class test {

    public static void main(String[] args) {
        String a = "hi";
        String b = "hey";
        String c = "hello";

        int len1 = a.length();
        int len2 = b.length();
        int len3 = c.length();
        int max = 0;
         if ( len1 > len2 && len1 > len3 )
                max = len1;
          else if ( len2 > len1 && len2 > len3 )
              max = len2;
          else if ( len3 > len1 && len3 > len2 )
              max = len3;

         for(int i=0; i<= max; i++) {
             char c1 = 0; char c2 = 0; char c3 = 0;
             //h,h,h
             //i,e,e
             //'',y,l
             //'','',l
             //'','',o
             printCharMerge(c1, c2, c3);
         }
    }

    public static void printCharMerge(char a, char b, char c) {
        System.out.println("A char val :"+ a + "B char val :"+ b + "C char val :"+ c);
    }
}

Any help and code improvement will be appreciated.

Answer 1

Perhaps this could help.

public class R
{
    public static void main(String[] args) {
        String a = "hi";
        String b = "hey";
        String c = "hello";

        int len1 = a.length();
        int len2 = b.length();
        int len3 = c.length();
        int max = 0;
        if ( len1 > len2 && len1 > len3 )
            max = len1;
        else if ( len2 > len1 && len2 > len3 )
            max = len2;
        else if ( len3 > len1 && len3 > len2 )
            max = len3;

        for(int i=0; i<= max; i++) {
            char c1 = 0; char c2 = 0; char c3 = 0;

            if(i >= a.length()) c1 = '\u0000';
            else c1 = a.charAt(i);

            if(i >= b.length()) c2 = '\u0000';
            else c2 = b.charAt(i);

            if(i >= c.length()) c3 = '\u0000';
            else c3 = c.charAt(i);

            printCharMerge(c1, c2, c3);
        }
    }

    public static void printCharMerge(char a, char b, char c) {
        System.out.println("A char val : '"+ a + "', B char val :'"+ b + "', C char val ':"+ c + "'");
    }
}

I've taken the liberty of modifying the output of printCharMerge a bit, so that it is clearly understood that the value printed is a null character.

Also, keep in mind that the default value of char is '\'

Logic -

If charAt(i) is called for a string (a, b, or c), and i is equal to or more than the length of that string, then a StringIndexOutOfBoundsException would be thrown.

Hence, if i is equal to or more than the length of that string, then the character becomes '\'

However: even this will print a space, because an empty char is printed as ' ' . So, you should use Strings everywhere like this:

public class R
{
    public static void main(String[] args) {
        String a = "hi";
        String b = "hey";
        String c = "hello";

        int len1 = a.length();
        int len2 = b.length();
        int len3 = c.length();
        int max = 0;
        if ( len1 > len2 && len1 > len3 )
            max = len1;
        else if ( len2 > len1 && len2 > len3 )
            max = len2;
        else if ( len3 > len1 && len3 > len2 )
            max = len3;

        for(int i=0; i<= max; i++) {
            String c1 = ""; String c2 = ""; String c3 = "";

            if(i >= a.length()) c1 = "";
            else c1 = ""+a.charAt(i);

            if(i >= b.length()) c2 = "";
            else c2 = ""+b.charAt(i);

            if(i >= c.length()) c3 = "";
            else c3 = ""+c.charAt(i);

            printCharMerge(c1, c2, c3);
        }
    }

    public static void printCharMerge(String a, String b, String c) {
        System.out.println("A char val : '"+ a + "',\tB char val : '"+ b + "',\tC char val : '"+ c + "'");
    }
}

And do note that \\t used in a string stands for horizontal tab :)

Answer 2

You are almost there, replace your for loop:

for(int i=0; i< max; i++) {
    String c1 = (a.length() <= i ? "" : a.substring(i, i + 1));
    String c2 = (b.length() <= i ? "" : b.substring(i, i + 1));
    String c3 = (c.length() <= i ? "" : c.substring(i, i + 1));
    System.out.println("A char val: "+ c1 + " B char val: "+ c2 + " C char val: "+ c3);
}

Also you can shorten the search for max value:

int max = Math.max(a.length(), Math.max(b.length(), c.length()));

Answer 3

First, you can declare multiple variables of the same type on one line by separating with a comma. Second, you can determine the maximum of three values by using nested calls to Math.max(int, int) . Third, you can use Character wrappers to store null (there is no "empty character"). Finally, you could use a ternary with a null guard in your print routine. Like,

public static void main(String[] args) {
    String a = "hi", b = "hey", c = "hello";
    int max = Math.max(a.length(), Math.max(b.length(), c.length()));
    for (int i = 0; i < max; i++) {
        Character x = i >= a.length() ? null : a.charAt(i), 
                y = i >= b.length() ? null : b.charAt(i),
                z = i >= c.length() ? null : c.charAt(i);
        printChar(x, y, z);
    }
}

public static void printChar(Character a, Character b, Character c) {
    if (a != null) {
        System.out.printf("A char val : %c ", a);
    }
    if (b != null) {
        System.out.printf("B char val : %c ", b);
    }
    if (c != null) {
        System.out.printf("C char val : %c", c);
    }
    System.out.println();
}

Outputs

A char val : h B char val : h C char val : h
A char val : i B char val : e C char val : e
B char val : y C char val : l
C char val : l
C char val : o

Answer 4

Use . charAt , like:

public class test {

    public static void main(String[] args) {
        String a = "hi";
        String b = "hey";
        String c = "hello";

        int len1 = a.length();
        int len2 = b.length();
        int len3 = c.length();
        int max = 0;
         if ( len1 > len2 && len1 > len3 )
                max = len1;
          else if ( len2 > len1 && len2 > len3 )
              max = len2;
          else if ( len3 > len1 && len3 > len2 )
              max = len3;

         for(int i=0; i<= max; i++) {
             char c1 = getChar(a, i); char c2 = getChar(b, i); char c3 = getChar(c, i);
             //h,h,h
             //i,e,e
             //'',y,l
             //'','',l
             //'','',o
             printCharMerge(c1, c2, c3);
         }
    }

    public static void printCharMerge(char a, char b, char c) {
        System.out.println("A char val :"+ a + "B char val :"+ b + "C char val :"+ c);
    }

    public static char getChar(String text, int index) {
        return (text.length() > index) ? text.charAt(index) : '\u0000';
    }
}