Array Lists

import java.util.ArrayList;  // Import the ArrayList class

ArrayList<String> stringList = new ArrayList<>();

stringList.add("Apple");
stringList.add("Banana");
stringList.add("Cherry");
stringList.add("Date");

//print out original size
System.out.println(stringList.size());

//add new element "Fig"
stringList.add("Fig");

//print out size
System.out.println(stringList.size());

//add new element "Grape" at index of 2
stringList.add(2,"Grape");

import java.util.ArrayList;  // Import the ArrayList class

class ArrayListHacks {
    private int findSum(ArrayList<Integer> values) {
        int sum = 0;
        for (Integer number : values){
            sum += number.intValue();
        }
        return sum;
    }

    public static void main(String[] args) {
        ArrayList<Integer> nums = new ArrayList<>();
        nums.add(0);
        nums.add(1);
        nums.add(2);
        nums.add(3);
        nums.add(5);
        nums.add(8);

        ArrayListHacks hacks = new ArrayListHacks();
        System.out.println(hacks.findSum(nums));
    }
}

ArrayListHacks.main(null);

19

import java.util.ArrayList;  // Import the ArrayList class

ArrayList<Double> weights = new ArrayList<>();
weights.add(4.5);
weights.add(2.1);
weights.add(-5.0);
weights.add(-1.9);
weights.add(-3.7);
weights.add(4.7);

ArrayList<Double> step(ArrayList<Double> array1){ 
    for(int i = 1; i < array1.size(); i++){
        if(array1.get(i-1) > array1.get(i)){
            Double temp = array1.get(i-1);
            array1.remove(i-1);
            array1.add(i,temp);
        }
    }
    return array1;
}

ArrayList<Double> sortArray(ArrayList<Double> array){
    boolean complete = false;
    while (!complete){
        for(int i = 1; i < array.size(); i++){
            if(array.get(i-1) > array.get(i)){
                array = step(array);
                break;
            }
            else if (i == array.size() - 1){
                complete = true;
            }
        }
    }
    return array;
}

weights = sortArray(weights);

System.out.println(Arrays.toString(weights.toArray()));

[-5.0, -3.7, -1.9, 2.1, 4.5, 4.7]

You could

userData = null;  //or new ArrayList<>();

ArrayList myList = new ArrayList();
myList.add("Hello");
myList.add("world,");
myList.add("my");
myList.add("favorite");
myList.add("color");
myList.add("is");
myList.add("red");

System.out.println(Arrays.toString(myList.toArray()));

ArrayList myList = new ArrayList();
myList.add("Hello");
myList.add("world,");
myList.add("my");
myList.add("favorite");
myList.add("color");
myList.add("is");
myList.add("red");

myList.set(1, "Del Norte");
System.out.println(Arrays.toString(myList.toArray()));

[Hello, Del Norte, my, favorite, color, is, red]

ArrayList myList = new ArrayList();
myList.add("Hello");
myList.add("world,");
myList.add("my");
myList.add("favorite");
myList.add("color");
myList.add("is");
myList.add("red");

myList.set(1, "Del Norte");

myList.remove(1);
System.out.println(Arrays.toString(myList.toArray()));

[Hello, my, favorite, color, is, red]

ArrayList myList = new ArrayList();
myList.add("Hello");
myList.add("world,");
myList.add("my");
myList.add("favorite");
myList.add("color");
myList.add("is");
myList.add("red");

System.out.println(myList.contains("Hello"));

true

ArrayList myList = new ArrayList();
myList.add("Hello");
myList.add("world,");
myList.add("my");
myList.add("favorite");
myList.add("color");
myList.add("is");
myList.add("red");

for(Object value: myList){
    System.out.println(value);
}

Hello
world,
my
favorite
color
is
red

ArrayList myList = new ArrayList();
myList.add(2);
myList.add(4);
myList.add(-3);
myList.add(7);
myList.add(1);
myList.add(5);
myList.add(3);

Collections.sort(myList);

System.out.println(Arrays.toString(myList.toArray()));

[-3, 1, 2, 3, 4, 5, 7]