Convert boolean[] to String and viceversa in java

Question

Howto convert a boolean array (or BitSet) to a string and vice versa.

Example:

boolean[] ar = {true,false,false,false,false};
print(BitArrayToString(ar));

Should return one of the following

10000 //binary
16 //decimal
10 //hex, prefered

The otherway around should work also

ar = StringToBitArray(BitArrayToString(ar));

Chii · Accepted Answer · 2009-12-14 13:37:06Z

3

long bitSetInt = 0;
for (int i = 0 ; i < ar.length ; i++) {
   bitSetInt = (bitSetInt | toDigit(ar[i])) << 1;
}
println(String.format("%x", bitSetInt));

where

int toDigit(boolean b) { return b?1:0;}

works as long as the ar array is less then the size of a long. Use http://java.sun.com/j2se/1.5.0/docs/api/java/util/Formatter.html#syntax for other formatting needs

answered Dec 14, 2009 at 13:37

Chii

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4 Comments

michiel Over a year ago

nice solution but I do not see how to do the reverse, the long size limitation might become a problem

Chii Over a year ago

because this smelt like homework, i didnt provide the full solution - just half. have a little think - its very easy to convert a digit into an array of bools.(and yes, the size limit of a long is indeed a problem, but the question didnt spec the max size...)

michiel Over a year ago

I have solved the size limitation by running the code for each 64bit block and concatinating the strings. thanks for your help

Chii Over a year ago

if that is the case, it might be better just to perform a loop, and use BigDecimal (instead of doing bit shifting)

Kico Lobo · Accepted Answer · 2009-12-14 13:38:11Z

2

Well, you could do something like this:

StringBuilder builder = new StringBuilder();
for (int i = 0; i < array.length; i++) {
    if (array[i]) builder.append("1"); else builder.append("0");
}
return builder.toString();

answered Dec 14, 2009 at 13:38

Kico Lobo

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1 Comment

michiel Over a year ago

this works but uses a lot more space then a hexadecimal solution.

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