5

I have two strings in a java program, which I want to mix in a certain way to form two new strings. To do this I have to pick up some constituent chars from each string and add them to form the new strings. I have a code like this(this.eka and this.toka are the original strings):

String muutettu1 = new String();
String muutettu2 = new String();
muutettu1 += this.toka.charAt(0) + this.toka.charAt(1) + this.eka.substring(2);
muutettu2 += this.eka.charAt(0) + this.eka.charAt(1) + this.toka.substring(2);
System.out.println(muutettu1 + " " + muutettu2);

I'm getting numbers for the .charAt(x) parts, so how do I convert the chars to string?

Thomas Jung
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rize
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5 Answers5

15
StringBuilder builder = new StringBuilder();
builder
   .append(this.toka.charAt(0))
   .append(this.toka.charAt(1))
   .append(this.toka.charAt(2))
   .append(' ')  
   .append(this.eka.charAt(0))
   .append(this.eka.charAt(1))
   .append(this.eka.charAt(2));
System.out.println (builder.toString());
alphazero
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  • I think, your result will be wrong. subString(2) is the string beginning with the index 2. – Thomas Jung Oct 31 '09 at 14:58
  • Yep, I missed that. Regardless, append is an overloaded method and you can pass it Strings as well. The salient point here was to not use String directly and use StringBuilder (or StringBuffer if on older JRE) to minimize the performance cost. – alphazero Oct 31 '09 at 15:22
  • a + b will be compiled to new StringBuilder().append(a).append(b).toString() anyway. – Thomas Jung Oct 31 '09 at 15:59
  • I really like this answer, but why not an enhanced `for` loop? eg. `for(String i : this.toka)` and do the same for `this.eka` – user1610406 Dec 13 '12 at 00:58
  • Try javap on both variants. (Haven't done it myself, but) likely the iterative form will peform superflous allocations for the 2 control structures (possibly unrolled by the compiler). Also do note that OP's Q did not indicate that the source Strings actually terminate at the indices provided, so it will need to be an explicit for loop form. – alphazero Dec 13 '12 at 03:09
7

The obvious conversion method is Character.toString.

A better solution is:

String muutettu1 = toka.substring(0,2) + eka.substring(2);
String muutettu2 = eka.substring(0,2) + toka.substring(2);

You should create a method for this operation as it is redundant.

The string object instatiantiation new String() is unnecessary. When you append something to an empty string the result will be the appended content.

Thomas Jung
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7

Just use always use substring() instead of charAt()


In this particular case, the values are mutable, consequently, we can use the built in String class method substring() to solve this problem (@see the example below):

Example specific to the OP's use case:

    muutettu1 += toka.substring(0,1) + toka.substring(1,2) + eka.substring(2);
   
    muutettu2 += eka.substring(0,1) + eka.substring(1,2) + toka.substring(2);

Concept Example, (i.e Example showing the generalized approach to take when attempting to solve a problem using this concept)

    muutettu1 += toka.substring(x,x+1) + toka.substring(y,y+1) + eka.substring(z);

    muutettu2 += eka.substring(x,x+1) + eka.substring(y,y+1) + toka.substring(z);
"...Where x,y,z are the variables holding the positions from where to extract."
JΛYDΞV
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jitter
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0

You can also convert an integer into a String representation in two ways: 1) String.valueOf(a) with a denoting an integer 2) Integer.toString(a)

htlbydgod
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-2

This thing can adding a chars to the end of a string

StringBuilder strBind = new StringBuilder("Abcd");
strBind.append('E');
System.out.println("string = " + str);
//Output => AbcdE
str.append('f');
//Output => AbcdEf
Chàrìthà SG
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