一次打印arraylist三个数字

Question

So I have an arraylist full of floats which currently prints on one line: -221.5, -301.6, 19.2, -249.3, -312.2, 19.7,.. etc

String arrayString = arr.toString();
arrayString= arrayString.substring(1,arrayString.length()-1); //Removes brackets
outputFile.println("array[]={"+arrayString+"};");

How do I format the arraylist so that it prints a new line every three numbers like:

-221.5, -301.6, 19.2, 
-249.3, -312.2, 19.7,
...

etc

Answer 1

Try using this...

public static void main(String[] args) {

    List<Float> floatList=new ArrayList<Float>();
    int i=0;

    floatList.add(-221.5f);
    floatList.add(-221.6f);
    floatList.add(-221.7f);
    floatList.add(-221.8f);
    floatList.add(-221.9f);
    floatList.add(-221.1f);
    for (Float float1 : floatList) {
        i++;
        System.out.print(" "+float1+",");
        if(i%3==0){
            System.out.println();
        }

    } 

Output:

-221.5, -221.6, -221.7,
-221.8, -221.9, -221.1,

Answer 2

Is a group of three numbers some meaningful quantity or entity in your application (they look like some kind of coordinate to me!)? If so just combine them into an object.

List<MyVector> list = new ArrayList<MyVector>;
list.add(new MyVector(-221.5, -301.6, 19.2));
list.add(new MyVector(-249.3, -312.2, 19.7));

for(MyVector v : list) {
    System.out.println(v.toString());
}

Otherwise use @x4rf41's suggestion.

Answer 3

for(int i=0;i<arr.length;i++) {
    outputFile.print(arr[i]+" ");
    if(i%3==2) {
        outputFile.println();
    }
}