Reading data into array from file

[r035198x]

I can run the class. But when I use "space delimited format" for an input file, I could not write all read data to a file. The read data are displayed normally when I write it to the console.

for (int i = 0; i < inWL[0].size(); i++) {
	System.out.println(inWL[0].get(i) + " " + inWL[1].get(i));
	fout1.write(inWL[0].get(i) + " " + inWL[1].get(i) + "\n");
}

By the way, how could I modify my code to read a file with "tab delimited format"?

public static ArrayList[] readFile2(String fileName) {
	 / * File Structure:
		 * 	1.1 11.1
		 * 	2.2 22.2
		 * 3.3 33.3
		 * 	... ... 
		 */	
			String line = " ";
			ArrayList[] data = new ArrayList[2];
 
			//for(int i = 0; i < 2; i++) {
			data[0] = new ArrayList<String>();
			data[1] = new ArrayList<Double>();
			//}
 
			try {
				FileReader fr = new FileReader(fileName);
				BufferedReader br = new BufferedReader(fr);
				while((line = br.readLine()) != null) {
					String[] theline = line.split(" ");
					data[0].add(theline[0]);
					data[1].add(Double.parseDouble(theline[1]));
 
					//System.out.println(data[0] + " " + data[1]);
				}
			}
			catch(FileNotFoundException fN) {
				fN.printStackTrace();
			}
 
			catch(IOException e) {
				System.out.println(e);
			}
 
			return data;
 
		} //end readFile2 method

The reading should be fine. It must be the line

String[] theline = line.split(" ");

Which is spilitting on space. You can split on any character

eg

 String[] theLine = line.split("\t");

to split on tab.

You said you could not print all the data to the other file but could print all the data to the console? If so then post the code you used for printing to the file.

[SkyGenius]

FileWriter fout1 = new FileWriter("output1.txt");
for (int i = 0; i < inWL[0].size(); i++) {
	System.out.println(inWL[0].get(i) + " " + inWL[1].get(i));
	fout1.write(inWL[0].get(i) + " " + inWL[1].get(i) + "\n");
}

[r035198x]

FileWriter fout1 = new FileWriter("output1.txt");
for (int i = 0; i < inWL[0].size(); i++) {
	System.out.println(inWL[0].get(i) + " " + inWL[1].get(i));
	fout1.write(inWL[0].get(i) + " " + inWL[1].get(i) + "\n");
}

I'd advise you the BufferedWriter class to write to a file

 
BufferedWriter out = new BufferedWriter(new FileWriter(file));
out.write(s);//writes the String s
out.newLine();//goes to next line

[SkyGenius]

Thanks so much for your advice.

[SkyGenius]

How could I do the operation on the ArrayList? Could I transfer all the element values in ArrayList[1] to an array?
The following is my problem. I could not do the calculation in the main method.

//This in main method

ArrayList[] inHAVCurve = new ArrayList[3];
String fin2 = "inHAVCurve.txt";
inHAVCurve = readFile3(fin2);

double[] a;
			
for (int i=0; i<inWL[0].size(); i++){
	a[i] = inHAVCurve[1].get(i) + inHAVCurve[2].get(i);
}

public static ArrayList[] readFile3(String fileName) {
	/* This method read file and store data in three ArrayLists[].   
	 * File Structure:
	 * 	1.1 11.1 111.1
	 * 	2.2 22.2 222.2
	 * 	3.3 33.3 333.3
	 * 	... ...  ...
	 */	
		String line = "\t";
		ArrayList[] data = new ArrayList[3];
		
		for(int i = 0; i < 3; i++) {
		data[i] = new ArrayList<Double>();
		}
		
		try {
			FileReader fr = new FileReader(fileName);
			BufferedReader br = new BufferedReader(fr);
			while((line = br.readLine()) != null) {
				String[] theline = line.split("\t");
				data[0].add(Double.parseDouble(theline[0]));
				data[1].add(Double.parseDouble(theline[1]));
				data[2].add(Double.parseDouble(theline[2]));
			}
		}
		catch(FileNotFoundException fN) {
			fN.printStackTrace();
		}
		
		catch(IOException e) {
			System.out.println(e);
		}
		
		return data;

	} //end readFile3 method

[r035198x]

How could I do the operation on the ArrayList? Could I transfer all the element values in ArrayList[1] to an array?
The following is my problem. I could not do the calculation in the main method.

 
//This in main method
 ArrayList[] inHAVCurve = new ArrayList[3];
String fin2 = "inHAVCurve.txt";
inHAVCurve = readFile3(fin2);
 
double[] a;
 
for (int i=0; i<inWL[0].size(); i++){
	a[i] = inHAVCurve[1].get(i) + inHAVCurve[2].get(i);
}
 
public static ArrayList[] readFile3(String fileName) {
	/* This method read file and store data in three ArrayLists[]. 
	 * File Structure:
	 * 	1.1 11.1 111.1
	 * 	2.2 22.2 222.2
	 * 	3.3 33.3 333.3
	 * 	... ... ...
	 */	
		String line = "\t";
		ArrayList[] data = new ArrayList[3];
 
		for(int i = 0; i < 3; i++) {
		data[i] = new ArrayList<Double>();
		}
 
		try {
			FileReader fr = new FileReader(fileName);
			BufferedReader br = new BufferedReader(fr);
			while((line = br.readLine()) != null) {
				String[] theline = line.split("\t");
				data[0].add(Double.parseDouble(theline[0]));
				data[1].add(Double.parseDouble(theline[1]));
				data[2].add(Double.parseDouble(theline[2]));
			}
		}
		catch(FileNotFoundException fN) {
			fN.printStackTrace();
		}
 
		catch(IOException e) {
			System.out.println(e);
		}
 
		return data;
 
	} //end readFile3 method

 ArrayList[] inHAVCurve  = readFile3(fin2); 
 
double[] a;
 
  for(int j = 0; j<inHAVCurve[1].size();j++) {
	a[i] = inHAVCurve[1].get(j) + inHAVCurve[2].get(j);
 }

For this to work, inHAVCurve[1] and inHAVCurve[2] must have the same number of elements.

[SkyGenius]

Yes, they have same number of elements. I tried it, but it still does not work. I got this in the console:

Exception in thread "main" java.lang.Error : Unresolved compilation problem:
The operator + is undefined for the argument type(s) java.lang.Objec t, java.lang.Objec t

[r035198x]

Yes, they have same number of elements. I tried it, but it still does not work. I got this in the console:

Exception in thread "main" java.lang.Error : Unresolved compilation problem:
The operator + is undefined for the argument type(s) java.lang.Objec t, java.lang.Objec t

You have to type cast the elements from the ArrayList to doubles like

 
a[i] = (Double)inHAVCurve[1].get(j) + (Double)inHAVCurve[2].get(j);

[SkyGenius]

It still cannot run. Index of a[j] is j, not i.

[r035198x]

It still cannot run. Index of a[j] is j, not i.

 
ArrayList[] inHAVCurve  = readFile3(fin2); 
double[] a = new double[inHAVCurve[0].size()];
for(int j = 0; j<inHAVCurve[1].size();j++) {
 a[j] = (Double)inHAVCurve[1].get(j) + (Double)inHAVCurve[2].get(j);
}

You should also put an effort of trying to correct some of the errors yourself.