Question About Java - Topic

Member

Posts: 856

Joined: Oct 10 2018

Gold: 0.00

Jan 30 2019 05:02am

Hey,

task: Calculate the sum over a list of integers. A loop should be used.

IS the following correct?

for (i = 1, i <= size(aListOfIntegers), i++) {
a = aListOfIntegers.get(i);
sum = sum + a)
}

thx

Klexmoo

Member

Posts: 12,703

Joined: May 17 2013

Gold: 12,935.00

Jan 30 2019 06:41am

Code

for (int number : aListOfIntegers) {
sum = sum + number;
}

You can just use the above definition instead, which loops over each number in the list and presents that directly to you.

Your example also has missing type information and a wrong method call:

Code

for (int i = 0; i < aListOfIntegers.size(); i++) {
int a = aListOfIntegers.get(i);
sum = sum + a;
}

Here's basically all the code you need:

Code

import java.util.ArrayList;
import java.util.List;

public class MyClass {
public static void main(String args[]) {
int sum = 0;
int sum2 = 0;
List<Integer> aListOfIntegers = new ArrayList<>();
aListOfIntegers.add(1);
aListOfIntegers.add(2);
aListOfIntegers.add(3);
aListOfIntegers.add(4);
aListOfIntegers.add(5);
aListOfIntegers.add(6);
aListOfIntegers.add(7);
aListOfIntegers.add(8);
aListOfIntegers.add(9);
aListOfIntegers.add(10);

for (int i = 0; i < aListOfIntegers.size(); i++) {
int a = aListOfIntegers.get(i);
sum = sum + a;
}

for (int number : aListOfIntegers){
sum2 += number;
}

System.out.println("Sum = " + sum);
System.out.println("Sum2 = " + sum2);
}
}

This post was edited by Klexmoo on Jan 30 2019 06:56am

05BB

Member

Posts: 856

Joined: Oct 10 2018

Gold: 0.00

Jan 30 2019 07:17am

Quote (Klexmoo @ Jan 30 2019 02:41pm)

Code

for (int number : aListOfIntegers) {
sum = sum + number;
}

You can just use the above definition instead, which loops over each number in the list and presents that directly to you.

Your example also has missing type information and a wrong method call:

Code

for (int i = 0; i < aListOfIntegers.size(); i++) {
int a = aListOfIntegers.get(i);
sum = sum + a;
}

Here's basically all the code you need:

Code

Thank you very much

Edit: Would it be possible to solve the task with a recursion ?

This post was edited by 05bb94 on Jan 30 2019 07:28am

Klexmoo

Member

Posts: 12,703

Joined: May 17 2013

Gold: 12,935.00

Jan 30 2019 08:53am

Quote (05bb94 @ 30 Jan 2019 14:17)

Thank you very much :)

Edit: Would it be possible to solve the task with a recursion ?

Yes, solving it with recursion would require a new function to be defined:

Code

public static int sumRecursive(List<Integer> numbers) {
if (numbers.isEmpty() == true ) {
return 0;
}
else {
return numbers.get(0) + sumRecursive(numbers.subList(1, numbers.size()));
}
}

The function takes one argument (the list of numbers to compute sum for) and adds the first number from the input list to the number obtained from a call to itself, on the remaining items from the input list.
A check is done on the list of numbers to end the recursion, since every recursion step decrements the size of the list by one.

This post was edited by Klexmoo on Jan 30 2019 08:55am

waraholic

Member

Posts: 1,039

Joined: Jul 8 2008

Gold: 1,939.50

Jan 30 2019 10:06pm

Code

aListOfIntegers.stream().mapToInt(Integer::intValue).sum()

Go Back To Programming & Development Topic List