从Java中的BufferReader读取字符字段

Question

how to read one line of chars in a field of chars in java?

private char[] w;
int i=0;

BufferedReader br = new BufferedReader(new FileReader("pathToFile..."));

char c = '-1';

while (c!='\n') {
    w[i++] = (char) br.read();
}

i got java.lang.NullPointerException

Answer 1

try this

 private char[] w;

 BufferedReader br = new BufferedReader(new FileReader("pathToFile..."));

 String s = null;
 // to iterate for each line in file
 while ((s = br.readLine()) !=  null ) {
    // this will store chars of line
    w = s.toCharArray();
   //TODO - do something based on w array

 }

Answer 2

You need to create an instance of the array (in Java, an array is an object -even if the array is of primitive types-)

private char[] w = new char[numberBigEnough];

Note that I would rather use a more dynamic approach, vg using a StringBuilder instance. That way you do not have to guess the line's length to specify the array dimensions.

Answer 3

I personally would use an ArrayList here.

private List<Character> list = new ArrayList<Character>();

int i=0;

BufferedReader br = new BufferedReader(new FileReader("pathToFile..."));

char c = '-1';

while (c!='\n') {
    list.add((char) br.read());
}

Something like that.