Java For loop within an array list

Im a beginner in java and starting to do test driven development. I have a pretty basic scenario i am stuck with. I want to pass a string of numbers from 1 to x. i.e if x is 3, it will return "1, 2, 3" or if x is 5, it will return "1, 2, 3, 4, 5".

I know that i need 开发者_JAVA百科to use an array list and a for loop but am stuck with the syntax. Someone please help!

Thanks

Try the following code:

int x = 5;

StringBuilder sb = new StringBuilder(); //You need import java.util.StringBuilder

for (int i = 1; i <= 5; i++) {
    sb.append(i);
    if (i!=x) {
        sb.append(',');
    }
}

String result = sb.toString(); //Here will be "1,2,3,4,5"

Here's a start:

String output = "";
int x = 5;

for (int i=1; i<=5; i++)
{
    output += i + ", ";
}

System.out.println(output);
// prints the string "1, 2, 3, 4, 5, "

String s = "";
int x = 5;

for(int i = 1; i <= x; i++) s += i + (i!=x?", ":"");

System.out.println(s); // It prints "1, 2, 3, 4, 5"

If it is a requirement to use array lists you can use the "add" and "get" methods in ArrayList:

List<Integer> listOfIntegers = new ArrayList<Integer>();

int = 5;
String stringOfIntegers = "";

for (int i = 1; i <= 5; i++) {
    listOfIntegers.add(i);
}

for (int i = 0; i < 5; i++) {
   stringOfIntegers += listOfIntegers.get(i);
   stringOfIntegers += ",";
}

System.out.println(stringOfIntegers);

ADDED: [Returned from a method]

public String numberString(){
    List<Integer> listOfIntegers = new ArrayList<Integer>();

    int = 5;
    String stringOfIntegers = "";

    for (int i = 1; i <= 5; i++) {
        listOfIntegers.add(i);
    }

    for (int i = 0; i < 5; i++) {
        stringOfIntegers += listOfIntegers.get(i);
        stringOfIntegers += ",";
    }

    return stringOfIntegers;
}

[Returned from a method where you tell it what number to count to]

public String numberString(int maxNumber){
    List<Integer> listOfIntegers = new ArrayList<Integer>();

    String stringOfIntegers = "";

    for (int i = 1; i <= maxNumber; i++) {
        listOfIntegers.add(i);
    }

    for (int i = 0; i < 5; i++) {
        stringOfIntegers += listOfIntegers.get(i);
        stringOfIntegers += ",";
    }

    return stringOfIntegers;
}

So for instance if you pass in a value of "7" the returned string will be: "1,2,3,4,5,6,7". To "invoke" this method you can use something like:

public static void main(String[] args){
    MyClass myClass = new MyClass(); //This will be the name of the class you created

    String myNumberString = myClass.numberString(6);

    System.out.println("My number string is: " + myNumberString); //This will print: "1,2,3,4,5,6"
}