CODEWITHSUNDEEP
javaarraylistcompiler-errorstype-conversion
nexus_2006
nexus_2006

Reputation: 754

Type mismatch: boolean[], Boolean[], ArrayList<Boolean>

I am trying to construct a boolean[][] from a text file. I am reading in each character, storing in an ArrayList (1s as true and 0s as false). I tried ArrayList, but got compile errors, unexpected element. So, I build an ArrayList, and try to store it in an ArrayList>. My last problem is with the type difference between boolean and Boolean in the following method. seedInProgress is the ArrayList> constructed by finishLine(). I am trying to copy it all out to a boolean[][] inside the for loop.

public void finishSeed(ArrayList<Boolean> lastLine) {
    finishLine(lastLine);
    seed = new boolean[seedInProgress.size()][seedInProgress.get(0).size()];
    for (int i = 0; i < seedInProgress.size(); i++ ) {
        seed[i] = seedInProgress.get(i).toArray()
    }
}

The error is: 

SeedFactory.java:75: error: incompatible types
            seed[i] = seedInProgress.get(i).toArray();
                                                   ^
  required: boolean[]
  found:    Object[]
1 error

but I can't cast it to boolean[], and Boolean[] is still an Object[].

How can I get a boolean[] from an ArrayList, or alternatively, how can I make an ArrayList?

Upvotes: 1

Views: 4858

Answers (2)

Bohemian
Bohemian

Reputation: 425083

Java won't autobox whole arrays at a time, if that is what you were hoping. Ie

boolean b;
Boolean B;
a = B; // OK
boolean[] bs;
Boolean[] Bs;
bs = Bs; // compiler error

But really why are you creating a List<Boolean> first? I would simply pass the line as a String, because it is a String. And your method is a bit too complicated - it does too much and knows about too much.

See if this method helps:

public static boolean[] toBooleanArray(String line) {
    boolean[] array = new boolean[line.length()];
    for (int i = 0; i < line.length(); i++ )
        array[i] = line.charAt(I) == '1';
    return array;
}

Your file could be then converted to a List<boolean[]> like this:

List<boolean[]> lines = new ArrayList<boolean[]>();
// loop reading "line" from file
    lines.add(toBooleanArray(line));

then to get a boolean[][]:

boolean[][] array = lines.toArray();

Upvotes: 1

Louis Wasserman
Louis Wasserman

Reputation: 198163

To get a lowercase boolean[] from an ArrayList<Boolean>, you have to do the for loop yourself, or use a utility method that does the same thing, a la Guava's Booleans.toArray.

The for loop is what you'd expect:

boolean[] array = new boolean[list.size()];
for (int i = 0; i < list.size(); i++) {
  array[i] = list.get(i);
}

Upvotes: 4

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