字符串中的正数和负数答案

【问题标题】：Positive and Negative numbers in String字符串中的正数和负数
【发布时间】：2014-12-19 16:03:04
【问题描述】：

我必须制作一个程序，允许用户输入整数，直到他按下“0”。该程序必须打印： 1)输入数字的总数 2）正数 3）正数的平均值 4）负数 5) 负数之和

到目前为止，我所能做的就是“输入直到按下'0'”并找到输入的数字的数量，这对我和我的编程技能来说非常重要。我在试图找出这个数字是正数还是负数时遇到了麻烦。可能我没有正确比较它们，所以如果我能从高级的人那里得到一点帮助，我会很高兴。

到目前为止，这是我的代码：

import java.io.*; 

class Nums { 
  public static void main(String args[])  
    throws IOException 
  { 
    BufferedReader br = new BufferedReader(new 
                            InputStreamReader(System.in)); 
    String str;
    int EnteredNumbers = -1;
    int Positive = 0;
    int Negative = 0;
    int NegativeSum = 0;
    double AveragePositive = 0;

    System.out.println("Enter '0' to quit."); 
    System.out.println("Enter Numbers: "); 
    do { 
      EnteredNumbers++;
      str = br.readLine();

    } while(!str.equals("0")); 
      System.out.println("You have have entered "+EnteredNumbers+ " numbers!");
      System.out.println("You have have entered "+Positive+ " Positive numbers!");
      System.out.println("The Average of the Positive Numebers is "+AveragePositive+ "!");
      System.out.println("You have have entered "+Negative+ " Negative numbers!");
      System.out.println("The Sum of the Negative numbers is "+NegativeSum+ "!");
  } 
}

【问题讨论】：

boolean isNeg=false; if(str.startsWith("-")){ str=str.substring(1); isNeg=true; } int NUMBER=Integer.parseInt(str); if(isNeg) { NUMBER*=-1; } 这样的事情？
顺便说一句，请注意命名变量的良好做法。他们不应该是资本

标签： java

【解决方案1】：

首先指出Integer.parseInt 在java 中用于将String 转换为int。其次，您还需要一个额外的变量来存储和累积正数的总数。我添加了一个try-catch 异常块来处理错误。

这里有一个代码供参考。

import java.io.*; 

public class Nums { 
  public static void main(String args[])  
    throws IOException 
  { 
    BufferedReader br = new BufferedReader(new 
                            InputStreamReader(System.in)); 
    String str;
    int EnteredNumbers = -1;
    int Positive = 0;
    int Negative = 0;
    int NegativeSum = 0;
    int PositiveSum = 0; // Added extra variable
    double AveragePositive = 0;

    System.out.println("Enter '0' to quit."); 
    System.out.println("Enter Numbers: "); 
   try{
    do { 
      EnteredNumbers++;
      str = br.readLine();

    int num = Integer.parseInt(str);


    if (num>0)
      {
        Positive++;
        PositiveSum+=num;
      }
      else if (num<0)
      {
        Negative++;
        NegativeSum+=num;
      }
    } while(!str.equals("0")); 
    AveragePositive = (double)PositiveSum/(double)Positive;
      System.out.println("You have have entered "+EnteredNumbers+ " numbers!");
      System.out.println("You have have entered "+Positive+ " Positive numbers!");
      System.out.println("The Average of the Positive Numebers is "+AveragePositive+ "!");
      System.out.println("You have have entered "+Negative+ " Negative numbers!");
      System.out.println("The Sum of the Negative numbers is "+NegativeSum+ "!");
    }
    catch (java.lang.NumberFormatException e)
    {
        System.out.println("Wrong format");
    }  

} 
}

如果没有错误则输出

Enter '0' to quit.
Enter Numbers: 
1
5
5
-5
-5
0
You have have entered 5 numbers!
You have have entered 3 Positive numbers!
The Average of the Positive Numebers is 3.6666666666666665!
You have have entered 2 Negative numbers!
The Sum of the Negative numbers is -10!

【讨论】：

你太棒了！只剩下一个问题 - 如果我输入双数字、一个字母或我只是按 Enter 程序应该给我一个无效格式消息...
另外，如果你输入：1 5 5 你得到 3 作为平均正数，它应该是 3.66
尝试输入 1 5 5 -5 -5 并检查平均值
@Monster 再次编辑。在计算平均值时进行了更改
非常感谢！现在完美了！

【解决方案2】：

通过将 String 解析为 int 来检查

Integer.parseInt(str)>0  //positive number
Integer.parseInt(str)<0 //negative



do { 
      EnteredNumbers++;
      str = br.readLine();
      int number= Integer.parseInt(str);
      if(number>0){  //do positive stuffs}
      else if(number<0){//do negative stuffs}
    } while(!str.equals("0"));

【讨论】：

我已经尝试过这样做，但似乎我在弄乱代码，因为它不断给我错误......

【解决方案3】：

希望下面的代码实现你想做的事情

import java.io.*; 

class Nums { 
  public static void main(String args[])  
    throws IOException 
  { 
    BufferedReader br = new BufferedReader(new 
                            InputStreamReader(System.in)); 
    String str;
    int EnteredNumbers = -1;
    int Positive = 0;
    int Negative = 0;
    int NegativeSum = 0;
    double AveragePositive = 0;
    double PositiveSum = 0;

    System.out.println("Enter '0' to quit."); 
    System.out.println("Enter Numbers: "); 
    do { 
      EnteredNumbers++;
      str = br.readLine();
      if(Integer.parseInt(str) > 0){
          Positive++;
          PositiveSum = PositiveSum + Integer.parseInt(str);
          AveragePositive = PositiveSum/Positive;
      }
      if(Integer.parseInt(str) < 0){
          Negative++;
          NegativeSum = NegativeSum + Integer.parseInt(str);
      }

    } while(!str.equals("0")); 
      System.out.println("You have have entered "+EnteredNumbers+ " numbers!");
      System.out.println("You have have entered "+Positive+ " Positive numbers!");
      System.out.println("The Average of the Positive Numebers is "+AveragePositive+ "!");
      System.out.println("You have have entered "+Negative+ " Negative numbers!");
      System.out.println("The Sum of the Negative numbers is "+NegativeSum+ "!");
  } 
}

【讨论】：

【解决方案4】：

创建一个列表并继续将数字添加到列表中。你应该这样做：

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

do { 
  str = br.readLine();
  int number = Integer.parseInt(str);
} while(number != 0);

然后使用 for 循环进行计数：

int negativeNumberSum = 0;
int positiveNumberSum = 0;
int positiveNumberCounts = 0;
for (int i =0; i<numberList.size(); i++) {
    if (numberList.get(i) >= 0) {
        positiveNumberSum += numberList.get(i);
        positiveNumberCounts ++;
    } else {
        negativeNumberSum += numberList.get(i);
    }
}

//print average of positive as positiveNumberSum /(double) positiveNumberCounts if positiveNumberCounts != 0
//print average of positive as negativeNumberSum / (double)(numberList.size() - positiveNumberCounts) same if (numberList.size() - positiveNumberCounts) != 0
//print positive count as positiveNumberSum  and same for negative.
//

【讨论】：

【解决方案5】：

尝试使用Integer.parseInt() 从字符串str 中获取int，并检查整数是< 0（负数）还是> 0（正数）

【讨论】：

【解决方案6】：

我添加了一个名为PositiveSum 的额外变量来协助AveragePositive 计算。

为了执行这个计算，你需要确保值是Integer，所以我添加了解析语句。

class Nums { 
  public static void main(String args[])  
    throws IOException 
  { 
    BufferedReader br = new BufferedReader(new 
                        InputStreamReader(System.in)); 
    String str;
    int EnteredNumbers = -1;
    int Positive = 0;
    int Negative = 0;
    int NegativeSum = 0;
    int PositiveSum = 0; 
    double AveragePositive = 0;

    System.out.println("Enter '0' to quit."); 
    System.out.println("Enter Numbers: "); 
    do { 
      EnteredNumbers++;
      str = br.readLine();
      int number = Integer.parseInt(str);
      if(number<0) {
          Negative++;
          NegativeSum += number;
      } else if(number>0) {
          Positive++;
          PositiveSum += number;

      }

    } while(!str.equals("0"));
      AveragePositive = PositiveSum / EnteredNumbers;
      System.out.println("You have have entered "+EnteredNumbers+ " numbers!");
      System.out.println("You have have entered "+Positive+ " Positive numbers!");
      System.out.println("The Average of the Positive Numebers is "+AveragePositive+ "!");
      System.out.println("You have have entered "+Negative+ " Negative numbers!");
      System.out.println("The Sum of the Negative numbers is "+NegativeSum+ "!");
  } 
}

【讨论】：

【解决方案7】：

更改您的do-while 循环：它使用的是字符串，而不是整数：

do { 
      EnteredNumbers++;
      num = sc.nextInt();

    } while(num != 0);

另外，您需要import scanner 实用程序：

import java.util.Scanner;

不要使用BufferedReader，而是使用：

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

此外，您可能希望在 do-while 循环中使用检查器检查正数和负数：

if(Integer.parseInt(num)<0) { Negative++; }
else { Positive++; }

我还添加了一个try-catch 语句来处理如果有人没有输入int 的错误：

      try {
      num = sc.nextInt();
      }
      catch(Exception e) {System.out.println("Invalid integer"); System.exit(0); }

我添加了一些代码，在打印数字时关闭0，因为我意识到当您输入退出时它将包含0。将你的class 语句更改为public，这只是编程：

public class Nums {

另外，我在主代码中添加了一个负数计数器和一个平均值。这是完整的代码，以避免混淆：

import java.io.*; 
import java.util.Scanner;
public class prime { 
  static Scanner sc = new Scanner(System.in);
  public static void main(String args[])  
  { 
    int EnteredNumbers = 0;
    int Positive = 0;
    int Negative = 0;
    int NegativeSum = 0;
    double AveragePositive = 0;
    int num = 0;
    int PosTotal = 0;
    System.out.println("Enter '0' to quit."); 
    System.out.println("Enter Numbers: "); 
    do { 
      try {
      num = sc.nextInt();
      }
      catch(Exception e) {System.out.println("Invalid integer!"); System.exit(0); }
      if(num<0) { Negative++; NegativeSum += num; }
      if(num>0){ Positive++; PosTotal += num; }
      EnteredNumbers++;
    } while(num != 0); 
      AveragePositive = PosTotal / Positive;
      EnteredNumbers -= 1;
      System.out.println("You have have entered "+EnteredNumbers+ " numbers!");
      System.out.println("You have have entered "+Positive+ " Positive numbers!");
      System.out.println("The Average of the Positive Numbers is "+AveragePositive+ "!");
      System.out.println("You have have entered "+Negative+ " Negative numbers!");
      System.out.println("The Sum of the Negative numbers is "+NegativeSum+ "!");
  } 
}

希望对您有所帮助！请注意，我已经对其进行了试用测试，并且效果很好。如果您对此有任何错误，请告诉我:)

【讨论】：