Question

我编写了以下代码，当我运行它时，它会以[＃，＃，＃，＃]的形式显示答案。我希望它显示为####（没有大括号和逗号）并且不使用system.out.print。不知何故，我想将结果存储在一个变量中，只需调用该变量。

import java.util.Scanner;

import java.util.ArrayList;

public class trial 

{

static Scanner keyboard = new Scanner(System.in);   

public static ArrayList<Integer> primeFactors(long number) 

{

        long n = number;
        ArrayList<Integer> factors = new ArrayList<Integer>();
        for (int i = 2; i <= n; i++) 
        {
            while (n % i == 0) 
            {
                factors.add(i);
                n /= i;
            }
        }

        return factors;

}
public static void main(String[] args) 
{
    System.out.println("Enter phone number to be factored");
    long input = keyboard.nextLong();

    System.out.println(primeFactors(input));
}
}

Answer 1

看一下它返回的内容https://docs.oracle.com/javase/7/docs/api/java/util/AbstractCollection.html#toString()

将其更改为

System.out.println(primeFactors(input)
          .toString().replace("[", "").replace("]", "").replace(",", " ");

或只是遍历并打印值

Answer 2

您可以在primeFactors方法中将返回类型更改为String。然后循环ArrayList并将内容添加到String中，如下所示。

package src.main;

import java.util.Scanner;

import java.util.ArrayList;

public class sampleMain

{

static Scanner keyboard = new Scanner(System.in);

public static String primeFactors(long number)

{

    long n = number;
    ArrayList<Integer> factors = new ArrayList<Integer>();
    for (int i = 2; i <= n; i++) {
        while (n % i == 0) {
            factors.add(i);
            n /= i;
        }
    }
    StringBuffer output = new StringBuffer();
    for (Integer integer : factors) {
        if( output.length()==0 ){
            output.append(integer.toString());
        }else{
            output.append(", "+integer.toString());
        }
    }
    return output.toString();

}

public static void main(String[] args) {
    System.out.println("Enter phone number to be factored");
    long input = keyboard.nextLong();

    System.out.println(primeFactors(input));
}
}

根据评论

更新 StringBuffer的答案

Answer 3

尝试迭代ArrayList中的值并将其附加到StringBuilder。像这样：

    StringBuilder oneStringValue = new StringBuilder();
    for(Integer tempNum : primeFactors(input)) {
        oneStringValue.append(tempNum.toString());
    }
    System.out.println(oneStringValue.toString());

这应该有效。

对于添加的信息，我使用StringBuilder附加字符串，因为它是mutable，而不是String immutable。

Answer 4

只需使用每个循环：

public static void main(String[] args) {
    Scanner keyboard = new Scanner(System.in);
    System.out.println("Enter phone number to be factored");
    long input = keyboard.nextLong();
    ArrayList<Integer> arr = primeFactors(input);
    for(int a:arr){
        System.out.print(a+" ");
    }
    keyboard.close();
}

如何在没有大括号的情况下显示ArrayList的元素

4 个答案: