“此方法必须返回int类型的结果” Java吗？

Question

public static void main(String args[])
{
    double arr[] = {1,-6.3,9000,67.009,1.1,0.0,-456,6,23,-451.88};

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

     List.add(1);
     List.add((int) -6.3);
     List.add(9000);
     List.add((int) 67.009);
     List.add((int)1.1);
     List.add((int)0.0);
     List.add(-456);
     List.add(6);
     List.add(23);
     List.add((int)451.88);
}

public static int ArrayListMax(ArrayList List)
{

    for (int i=0; i<List.size(); ++i)
    {
        System.out.println(List.get(i));
    }

The error is in:

  public static int ArrayListMax(ArrayList List) 

This is probably a very nooby mistake, but I'm new to Java so forgive me.

Any help please?

Thank you.

EDIT:

I want the ArrayListMax method to print the size of the List!

Answer 1

Either add a return statement to your ArrayListMax() method that returns an int or change the method signature from public static int to public static void . And add a closing } to the method too.

Also, you shouldn't use List as a name for the argument to that method because it's the name of an interface that you're actually importing in this code. The convention in java is for variable names and method names to begin with a lowercase letter (camel case) and class names to begin with an uppercase letter (pascal case).

Answer 2

Assuming you are trying to get the maximum value in your List in the method arrayListMax , you need to return an integer in accordance with your method signature, which the error is telling you

This method must return a result of type int

Instead of printing all the values in the list, you could do:

public static int arrayListMax(List<Integer> List) {
   return Collections.max(list);
}

---

Use Java Naming Conventions . Method & variable names begin with a lowercase letter. Using this approach helps avoid confusion between instances & types (eg in the case of List in the main method).

Answer 3

Problem is in this method:

public static int ArrayListMax(ArrayList List)
{

    for (int i=0; i<List.size(); ++i)
    {
       System.out.println(List.get(i));
    }
}

You are not returning from this method, you must return of type int to solve that error. Since you have specified int as return type.

Answer 4

You created the function as returning a result

public static int ArrayListMax(ArrayList List) 

In order to remove your problem, if you need not return anything, write

public static void ArrayListMax(ArrayList List) 

void means you do not want the method to return a result.

Answer 5

如果您只是打印出值，则签名应为公共静态void ArrayListMax（ArrayList List）。

Answer 6

First , you are not returning anything with ArrayListMax method even if you have set its retun type to int . Either return void as you are directly printing from the list.

Second, even if you set the correct return type to ArrayListMax method, you will still need to call that method in the main method as below:

public static void main(String args[])
{
    double arr[] = {1,-6.3,9000,67.009,1.1,0.0,-456,6,23,-451.88};

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

     List.add(1);
     List.add((int) -6.3);
     List.add(9000);
     List.add((int) 67.009);
     List.add((int)1.1);
     List.add((int)0.0);
     List.add(-456);
     List.add(6);
     List.add(23);
     List.add((int)451.88);
     YourClassNameInWhichMethodIs.ArrayListMax(List);
}

Answer 7

您应该使用return语句，因为Methode返回的是int类型值。