introduce

A Java program to calculate the sum of numbers in a list using while loop is a simple program that takes a list of integers and calculates their sum using a while loop structure. In this program, an ArrayList of integers is created and some numbers are added to the list. The program then uses a while loop to iterate through each element in the list, adding each element to the variable "sum", which keeps track of the running sum of the numbers. After the loop completes, the final value of "sum" is printed to the console, which is the sum of all the numbers in the list.

This program demonstrates a common technique for working with data collections in programming, which is to use a loop to iterate over each element in the collection and perform some calculation or transformation on each element. The program also highlights the use of ArrayList in Java, a common data structure used to store collections of data.

Example 1

method

• First, we create an integer ArrayList named "numbers" and add some numbers to it. In this program we add the numbers 1, 2, 3, 4 and 5 to the list.

• Then we declare two variables - "sum" and "i". "sum" is initialized to 0 because we want to sum the numbers starting from zero. "i" is initialized to 0 because this is the index of the first number in the list that we want to start adding to the sum.

• We start a while loop that will continue execution as long as "i" is less than the size of the list. The size of the list can be obtained using the "size" method of the ArrayList class.

• Within the loop, we use the "get" method of the ArrayList class to retrieve the current number in the list and add it to the sum. We then increase "i" by 1 to move to the next number in the list.

• After the loop completes, we have calculated the sum of all the numbers in the list. We print out the sum using the "println" method.

In general, this method is relatively simple and straightforward. It uses a while loop to iterate over the elements of the list and accumulate their sum into a separate variable. This is a common technique in programming for working with lists and other data collections.

This is a Java program that uses a while loop to calculate the sum of numbers in a list -

import java.util.ArrayList;

public class SumOfListUsingWhileLoop {
   public static void main(String[] args) {
      ArrayList<Integer> numbers = new ArrayList<Integer>();
      numbers.add(1);
      numbers.add(2);
      numbers.add(3);
      numbers.add(4);
      numbers.add(5);

      int sum = 0;
      int i = 0;

      while (i < numbers.size()) {
         sum += numbers.get(i);
         i++;
      }

      System.out.println("The sum of the numbers in the list is: " + sum);
   }
}

illustrate

In this program, we first create an integer ArrayList named "numbers" and add some numbers to it. We then declare two variables: "sum" (initialized to 0), which stores the sum of the numbers in the list, and "i" (initialized to 0), which keeps track of the current value we are adding to the sum. Numeric index.

Next, we start a while loop that continues as long as "i" is less than the size of the list. Inside the loop, we add the current number in the list (retrieved using the "get" method) to the sum and increment "i" to move to the next number in the list.

Finally, once the loop ends, we use the "println" method to print out the sum of the numbers in the list.

Output

The sum of the numbers in the list is: 15

Example 2

method

• First, we create an ArrayList of Double values ??called "numbers" and add some numbers to it. In this program we add the numbers 2.5, 3.7, 1.8, 4.2 and 2.9 to the list.

• Then we declare two variables: "sum" and "i". "sum" is initialized to 0.0 because we want to sum the numbers starting from zero. "i" is initialized to 0 because this is the index of the first number in the list where we want to start adding numbers to the sum.

• We start a while loop that will continue execution as long as "i" is less than the size of the list. The size of the list can be obtained using the "size" method of the ArrayList class.

• Within the loop, we use the "get" method of the ArrayList class to retrieve the current number in the list and add it to the sum. We then increase "i" by 1 to move to the next number in the list.

• After the loop completes, we have calculated the sum of all the numbers in the list. We print out the sum using the "println" method.

Overall, the methods used in this program are very similar to those used in the previous examples. We use a while loop to iterate over the elements of the list and accumulate their sum into a separate variable. However, in this case, we use a Double value instead of an Integer value, which allows us to include decimal places in the number. Additionally, we use a different set of numbers in the list to demonstrate that the program can handle a variety of input values.

This is another example of a Java program that uses a while loop to calculate the sum of numbers in a list -

import java.util.ArrayList;

public class SumOfListUsingWhileLoop2 {
   public static void main(String[] args) {
      ArrayList<Double> numbers = new ArrayList<Double>();
      numbers.add(2.5);
      numbers.add(3.7);
      numbers.add(1.8);
      numbers.add(4.2);
      numbers.add(2.9);

      double sum = 0.0;
      int i = 0;

      while (i < numbers.size()) {
         sum += numbers.get(i);
         i++;
      }

      System.out.println("The sum of the numbers in the list is: " + sum);
   }
}

illustrate

In this program, we create an ArrayList of Double values ??called "numbers" and add some numbers to it. We then declare two variables: "sum" (initialized to 0.0) to store the sum of the numbers in the list, and "i" (initialized to 0) to keep track of the index sum of the current number we want to add to.

接下來，我們啟動一個 while 循環(huán)，只要“i”小于列表的大小，該循環(huán)就會繼續(xù)。在循環(huán)內(nèi)，我們將列表中的當前數(shù)字（使用“get”方法檢索）添加到總和中，并遞增“i”以移至列表中的下一個數(shù)字。

最后，一旦循環(huán)結(jié)束，我們使用 "println" 方法打印出列表中數(shù)字的總和。請注意，在這個例子中，我們使用的是 Double 值而不是 Integer 值，這允許我們在數(shù)字中包含小數(shù)位。

輸出

The sum of the numbers in the list is: 1.5

結(jié)論

• 在本文中，我們討論了兩個使用while循環(huán)計算列表中數(shù)字總和的Java程序示例。在這兩個示例中，我們使用了類似的方法來迭代列表中的每個元素，在一個單獨的變量中累加它們的總和，然后輸出結(jié)果。

• 我們還討論了這些程序的時間和空間復(fù)雜度。這兩個程序的時間復(fù)雜度都是 O(n)，其中 n 是列表中元素的數(shù)量，因為我們需要迭代列表中的每個元素來計算它們的總和。兩個程序的空間復(fù)雜度都是 O(1)，因為我們只需要使用幾個變量來存儲輸入列表、運行總和以及循環(huán)計數(shù)器，并且這些變量的大小不依賴于輸入。

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