Finding Largest String in ArrayList

问题

// Im trying to find the largest String in my ArrayList and print it out and also to include what index the largest element resides at and to print that to screen too. Im just wondering where Im going wrong.

Thanks.

import java.util.Scanner;                  
import java.util.ArrayList;

public class ArraylistString
{
   public static void main(String [] args)
   {
    // Instance of Scanner class
      Scanner keyboardIn = new Scanner(System.in);

   // Declare an array list of Strings
      ArrayList<String> Str = new ArrayList<>();
   // Add names to ArrayList
      Str.add("Jim Bob");
      Str.add("Bobby Jones");
      Str.add("Rob Stiles");
      int largestString = Str.size();
      int index = 0;

   // Use for loop to print out elements from ArrayList
      for(int i = 0; i < Str.size(); i++)
      {  // Test which String is the largest
         if(Str[i].size() > largestString)
         {
            largestString = Str[i].size();
            index = i;
         }

      } 
      // Output largest String and index it was found at
      System.out.println("Index " + index + " "+ Str[index] + " " + "is the largest and is size " + largestString);  

   }

}

回答1:

Please try these code . Here i am trying with get() to access the ArrayList elements, which is working correctly.

import java.util.Scanner;                  
import java.util.ArrayList;

class ArraylistString
{
    public static void main(String args[])
    {
        ArrayList<String> Str = new ArrayList<String>();
        Str.add("Jim Bob");
        Str.add("Bobby Jones");
        Str.add("Rob Stiles");
        int largestString = Str.get(0).length();
        int index = 0;

        for(int i = 0; i < Str.size(); i++)
        {
            if(Str.get(i).length() > largestString)
            {
                largestString = Str.get(i).length();
                                index = i;
            }
        }
        System.out.println("Index " + index + " "+ Str.get(index) + " " + "is the largest and is size " + largestString);  

    }

}

回答2:

You can also use java.util.Collections.max.

Java 8

String max = Collections.max(Str, Comparator.comparing(String::length)); // or s -> s.length()

Prior Java 8

String max = Collections.max(Str, new Comparator<String>() {
    @Override
    public int compare(String o1, String o2) {          
        return o1.length() - o2.length();
    }
});

Then

 System.out.println("Index " + arr.indexOf(max) + " " + max + " " + "is the largest and is size " + max.length());

回答3:

You have the correct idea, but wrong syntax. In Java, only arrays support the [] syntax. An ArrayList isn't an array, it's a class that implements the List interface, and you should use the get method to access its members. Similarly, a String doesn't have a size() method, it has a length() method.

回答4:

I would set your largestString variable to your first String that you add:

int largestString = Str.get(0).length();

Then you should use the following to check for the largest String:

if(Str.get(i).length() > largestString) {
    largestString = Str.get(i).length();
    index = i;
}

You cannot index into an ArrayList with [] as you were trying to do.

I would also suggest better variable names. If I saw Str as a variable I would think it was a String. Maybe try strList or something like that.

回答5:

From Java-8 and onwards:

    List<Integer> numList = Arrays.stream(Str).map(String::length).collect(Collectors.toList());
    Integer m = numList.stream().mapToInt(i->i).max().orElse(4000);  //get strings with their length
    int k = numList.indexOf(m);  //index of String with Maximum Length
    System.out.println(Str.get(k)); //get your longest string

回答6:

What are you getting as output?

also, the line

int largestString = Str.size()

is setting largestString as the number of elements in the array Str so that may cause errors. I would set it to 0 or even -1 as a baseline, or maybe Str[0].size() so that you can start your for loop with your first element as your baseline.

EDIT:

I didn't even realize this was Java so like what people are saying, you cannot use the [] operator as you can in most languages and you should use string.length() not str.size()

来源：https://stackoverflow.com/questions/32593820/finding-largest-string-in-arraylist

标签

java

arraylist