This is the code I have and essentially I want to write this into a csv file:

ArrayList <String> course = new ArrayList<>();
ArrayList <String> name = new ArrayList<>();
ArrayList <Integer> age = new ArrayList<>();

File file = new File("jj.csv");
FileWriter fw = new FileWriter(file);
BufferedWriter bw = new BufferedWriter(fw);

bw.write("Course,Name,Age");
bw.newLine();
for (int i = 0; i < course.size(); i  ) {
    bw.write(course.get(i));
    bw.newLine();
}


for (int i = 0; i < name.size(); i  ) {
    bw.write(","   name.get(i));
    bw.newLine();
}

for (int i = 0; i < age.size(); i  ) {
    bw.write(","   age.get(i));
    bw.newLine();
}

bw.close();
fw.close();

I want the output to be in this format, I'm getting an output where the second and third-row are all over the place :

Course   Name    Age
math     john    7
english  bob     9

CodePudding user response：

Try to remove the insertion of a newline after each write and use one loop, I will assume the three lists have the same size

for(int i=0;i<course.size();i  ) {
    bw.write(course.get(i));
    bw.write("," name.get(i));
    bw.write("," age.get(i));
    bw.newLine();
}
bw.close();
fw.close();

, or use in one-line

for(int i=0;i<course.size();i  ) {
    bw.write(course.get(i)   "," name.get(i)   "," age.get(i));
    bw.newLine();
}
bw.close();
fw.close();

CodePudding user response：

As best as I can tell from your question, you can do it like this. It writes to the file and to the console.

Some data

List<String> course = List.of("math", "english", "chemistry");
List<String> name = List.of("John", "Mary", "James");
List<Integer> age = List.of(19, 20, 20);

// file destination and format string
File file = new File("jj.csv");
String format = "%-10s %-8s %-4s%n";

• This uses try-with-resources to open and close the writer.
• Process the lists in a single loop
  • put the values in an array for joining with String.join
  • and use System.printf to format them to the console.

try (BufferedWriter bw =
        new BufferedWriter(new FileWriter(file))) {
    bw.write("Course,Name,Age");
    
    System.out.printf(format, "Course", "Name",
            "Age");
    for (int i = 0; i < course.size(); i  ) {
        String s =
                String.join(",", new String[] { course.get(i),
                        name.get(i), age.get(i)   "" });
        System.out.printf(format, course.get(i),
                name.get(i), age.get(i));
        bw.write(","  s);
    }
} catch (Exception e) {
    e.printStackTrace();
}

CodePudding user response：

I think use MessageFormat.format() method(it's in java.text package) is a good solution.This is a example:

@Test
    public void test05(){
        final String formatTemplate = "{0},{1},{2}";
        List<String> course = Arrays.asList("course0","course1");
        List <String> name = Arrays.asList("name0","name1");
        List <Integer> age = Arrays.asList(1,2);
        final int size = course.size();
        for (int i = 0; i < size; i  ) {
            final String lineString = MessageFormat.format(formatTemplate, course.get(i), name.get(i), age.get(i));
            System.out.println(lineString);
            //TODO: bw.write(linString);bw.newLine();
        }
    }

Can get:

course0,name0,1
course1,name1,2