使用 java 创建二维 arraylist

Question

I want to add values in two dimensional arraylist using java. I am using this code

public abstract class TwoDimensionalArrayList {

public static void main(String[] args) {
    ArrayList<ArrayList<String>> twoDimensional=new ArrayList<>();
    oneDimensional.add(new ArrayList<String>());
    int value=0;
    for(int i=0;i<3;i++) {
        for(int j=0;j<3;j++) {
            twoDimensional.get(i).add(value+"");
            value++;
        }
    }
    for(int i=0;i<3;i++) {
        for(int j=0;j<3;j++) {
            System.out.println(twoDimensional.get(i).get(j));
        }
    }
}

}

I want to output as

twoDimensional={{1,2,3},{4,5,6},{7,8,9}}

when i run my code i am getting error like this.

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index 1 out of bounds for length 1
at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)
at java.base/java.util.Objects.checkIndex(Objects.java:373)
at java.base/java.util.ArrayList.get(ArrayList.java:425)
at TwoDimensionalArrayList.main(TwoDimensionalArrayList.java:11)

Please anyone help me

Answer 1

I'm assuming that there's a typo in the code, and that oneDimensional.add(...) should actually be twoDimensional.add(...) in which case, the first loop runs from i=0 to i=2, but you've only added one ArrayList to twoDimensional. This triggers an IndexOutOfBoundsException