Java completes a line read from a file

Question

So, I have a file that reads integers from a file that looks like this. 123456-1324563 .

The file reads these numbers as a string, and I'm trying to figure out how to create a method that adds the number 0 to the side of the read number that is less than the other.

For example, if there are fewer numbers on the left side of the operator than on the right, it will add 0 to the line so that these two numbers become even and return a new line. So I need a method to turn a String like 123456789-123456 into 123456789-000123456 . But he will need to determine which side is shorter, and in front of him - pad 0, but still returns the entire string.

Edit:

This is my most updated version of this method that I use, and when the + operator is passed, I get an ArrayIndexOutOfBoundsException . But it works great with the operator - .

 public String pad(String line, String operator){ String str[] = line.split(Pattern.quote(operator)); StringBuilder left = new StringBuilder(str[0]); StringBuilder right = new StringBuilder(str[1]); left = left.reverse(); right = right.reverse(); int len1 = left.length(); int len2 = right.length(); if(len1>len2){ while(len1!=len2){ right.append("0"); len1--; } }else{ while(len1!=len2){ left.append("0"); len2--; } } return left.reverse().toString()+operator+right.reverse().toString(); } 

Answer 1

A simple solution:

 public static String pad_num(String line){ String[] groups = line.split("-"); String left = groups[0], right = groups[1]; if(left.length() < right.length()) { do { left = '0'+left; } while (left.length() < right.length()); } else if(right.length() < left.length()) { do { right = '0'+right; } while (right.length() < left.length()); } return left+'-'+right; } 

---

If you do not have a fixed operator, you can pass it as an argument:

 public static String pad_num(String line, String operator){ //prevent ArrayIndexOutOfBoundsException if(!line.contains(operator)) { return line; } //prevent PatternSyntaxException by compiling it as literal String[] groups = Pattern.compile(operator, Pattern.LITERAL).split(line); //do the same ... return left+operator+right; } 

Answer 2

Using java 8 , a more concise and compact version

 public String pad_num(String line, String operator){ String str[] = line.split(Pattern.quote(operator)); char []buff = new char[Math.abs(str[0].length()-str[1].length())]; Arrays.fill(buff, '0'); if(str[0].length()>str[1].length()){ return String.join(operator, str[0], new StringBuilder(String.valueOf(buff)).append(str[1])); }else{ return String.join(operator, new StringBuilder(String.valueOf(buff)).append(str[0]), str[1]); } } 

If you do not have java8, use this implementation of your method

 public String pad_num(String line, String operator){ String str[] = line.split(Pattern.quote(operator)); StringBuilder left = new StringBuilder(str[0]); StringBuilder right = new StringBuilder(str[1]); left = left.reverse(); right = right.reverse(); int len1 = left.length(); int len2 = right.length(); if(len1>len2){ while(len1!=len2){ right.append("0"); len1--; } }else{ while(len1!=len2){ left.append("0"); len2--; } } return left.reverse().toString()+operator+right.reverse().toString(); } 

And call this method like

 String result = pad_num("123456+1324563", "+"); String result = pad_num("123456-1324563", "-"); 

Edit:

The reason ArrayIndexOutOfBoundsException is a method call with mismatch arguments, e.g.

 pad_num("123456-1324563", "+"); // - in line and + in operator 

or

 pad_num("123456+1324563", "-"); // + in line and - in operator 

Answer 3

You can do it:

 public String pad_num(String line){ String[] lines = line.split("-"); String s1=lines[0]; String s2=lines[1]; StringBuilder sb = new StringBuilder(); if(s1.length() == s2.length()){ return line; }else if(s1.length() > s2.length()){ sb.append(s1); sb.append("-"); for(int i=0;i<s1.length()-s2.length();i++){ //add zeros before s2 sb.append("0"); } sb.append(s2); }else{ for(int i=0;i<s2.length()-s1.length();i++){ //add zeros before s1 sb.append("0"); } sb.append(s1); sb.append("-"); sb.append(s2); } return sb.toString(); } 

Answer 4

These solutions work. Just an alternative using Apache StringUtils.

 public static String pad_num(String line){ String paddedStr = null; String[] numbers = StringUtils.split(line, "-"); if(numbers == null || (numbers[0].length() == numbers[1].length())) { return line; } if(numbers[0].length() > numbers[1].length()) { paddedStr = numbers[0] + "-" + StringUtils.leftPad(numbers[1], numbers[0].length(), "0"); } else { paddedStr = StringUtils.leftPad(numbers[0], numbers[1].length(), "0") + "-" + numbers[1]; } return paddedStr; } 

Answer 5

In "real life" (unless it's homework), you should use the library for this purpose. For example, using Guava Strings.padStart() , the method is simplified:

 import static com.google.common.base.Strings.padStart; /* ... */ public String pad(String line, String delim, char padding) { String[] tokens = line.split(delim); int[] lengths = new int[] {tokens[0].length(), tokens[1].length()}; return lengths[0] > lengths[1] ? tokens[0] + delim + padStart(tokens[1], lengths[0], padding) : lengths[0] < lengths[1] ? padStart(tokens[0], lengths[1], padding) + delim + tokens[1] : line; } 

Some test runs with code

 System.out.println(pad("123456-1324563", "-", '0')); System.out.println(pad("1324563-123456", "-", '0')); System.out.println(pad("123456789-123456", "-", '0')); System.out.println(pad("123456-123456", "-", '0')); 

Output

  0123456-1324563
 1324563-0123456
 123456789-000123456
 123456-123456

Answer 6

As others have already told you, use lib to do this ( Guava / Apache StringUtils ).

Another example of how to do this manually if you insist:

 String pad(String s) { String[] parts = s.split("-"); int n = parts[0].length() - parts[1].length(); return n < 0 ? String.format("%s%s-%s", zeros(Math.abs(n)), parts[0], parts[1]) : String.format("%s-%s%s", parts[0], zeros(Math.abs(n)), parts[1]); } 

(And this zero-util ...)

 String zeros(int numZeros) { char[] chars = new char[numZeros]; Arrays.fill(chars, '0'); return new String(chars); }