How to assign a String from a text file into integer array for Java?

Question

How to assign a String from a text file into integer array for Java? I had saved the integer array into a text file, but now how can I retrieve all the integer array from the text file without any modification? I want the integer array retrieved same as before it stored into the text file. Below is part of my code:

BufferedWriter f1 = new BufferedWriter(new InputStreamReader(new FileInputStream("Input.txt")));

int a[ ] = yes(test, test.length); //go to yes method,return value to array  
for(int i = 0; i < a.length; i++)  
{  
    f1.write(a[i]);  
}  
    f1.close( );  

BufferedReader f2 = new BufferedReader(new InputStreamReader(new FileInputStream("Input.txt")));  
String src;  
while((src = f2.readLine( )) != null)  
{  
    String[ ] s = src;  
    int a[ ] = Integer.parseInt(s);//same with before it saved  
    ... ...  
}

(incompatible types found)
How to reserve the originality of the integer array(a[ ]) after saved and retrieved from the text file? Thanks!

Answer 1

You need to somehow separate the integers. The simplest solution is to write each one in a separate line. Or use a comma separated list and then use String.split(",")

Answer 2

The way you have written the characters is totally wrong, you are writing the character representation of the int. Internally this is written as a char. You need to write your integers like so.

for(int i = 0; i < a.length; i++)
{
   String value = String.valueOf(a[i]);
   f1.println(value);
}

This should be compatible with how you are now reading your integers.

Answer 3

This looks like homework. Anyway, here's my test code:

// Write integers to a file, each on a different line
BufferedWriter f1 = new BufferedWriter( new FileWriter( new File( "Input.txt" ) ) );
int a[] = new int[]{ 17 , 42 , 37 };
for ( int i = 0 ; i < a.length ; i++ ) {
  f1.write( String.valueOf( a[ i ] ) + "\r\n" );
}
f1.close();

// Read integers from a file, assume each value on a different line
final BufferedReader bufferedReader = new BufferedReader( new FileReader( new File( "Input.txt" ) ) );
String line;
final List< Integer > values = new ArrayList< Integer >();
while ( ( line = bufferedReader.readLine() ) != null ) {
  values.add( Integer.valueOf( line ) );
}
bufferedReader.close();

// Convert List elements to array
final int[] valueArray = new int[ values.size() ];
int counter = 0;
for ( int value : values ) {
  valueArray[ counter ] = value;
  counter++;
}

// Print array values
for ( int value : valueArray ) {
  System.out.println( "value: |" + value + "|" );
}

The output is as follows

value: |17|
value: |42|
value: |37|