Java 在循环中同时打印两个字符串，但在单独的；段落；

头等舱：

public class Pets
{
    // Instance variables
    private String name;
    private int age;             //in years
    private double weight;       //in pounds

    // Default values for instance variables
    private static final String DEFAULT_NAME = "No name yet." ;
    private static final int DEFAULT_AGE = -1 ;
    private static final double DEFAULT_WEIGHT = -1.0 ;

   /***************************************************
    * Constructors to create objects of type Pet
    ***************************************************/

    // no-argument constructor
    public Pets()
    {
        this(DEFAULT_NAME, DEFAULT_AGE, DEFAULT_WEIGHT) ;
    }
    // only name provided
    public Pets(String initialName)
    {
        this(initialName, DEFAULT_AGE, DEFAULT_WEIGHT) ;
    }
    // only age provided
    public Pets(int initialAge)
    {
        this(DEFAULT_NAME, initialAge, DEFAULT_WEIGHT) ;
    }
    // only weight provided
    public Pets(double initialWeight)
    {
        this(DEFAULT_NAME, DEFAULT_AGE, initialWeight) ;
    }
    // full constructor (all three instance variables provided)
    public Pets(String initialName, int initialAge, double initialWeight)
    {
        setName(initialName) ;
        setAge(initialAge) ;
        setWeight(initialWeight) ;
    }

   /****************************************************************
    * Mutators and setters to update the Pet.  Setters for age and
    * weight validate reasonable weights are specified
    ****************************************************************/

    // Mutator that sets all instance variables
    public void set(String newName, int newAge, double newWeight)
    {
        setName(newName) ;
        setAge(newAge) ;
        setWeight(newWeight) ;
    }

    // Setters for each instance variable (validate age and weight)
    public void setName(String newName)
    {
        name = newName;
    }
    public void setAge(int newAge)
    {
        if ((newAge < 0) && (newAge != DEFAULT_AGE))
        {
            System.out.println("Error: Invalid age.");
            System.exit(99);
        }
        age = newAge;
    }
    public void setWeight(double newWeight)
    {
        if ((newWeight < 0.0) && (newWeight != DEFAULT_WEIGHT))
        {
            System.out.println("Error: Invalid weight.");
            System.exit(98);
        }
        weight = newWeight;
    }

   /************************************
    * getters for name, age, and weight
    ************************************/
    public String getName( )
    {
        return name ;
    }
    public int getAge( )
    {
        return age ;
    }
    public double getWeight( )
    {
        return weight ;
    }

   /****************************************************
    * toString() shows  the pet's name, age, and weight
    * equals() compares all three instance variables
    ****************************************************/
    public String toString( )
    {
        return ("Name: " + name + "  Age: " + age + " years"
                       + "   Weight: " + weight + " pounds");
    }
    public boolean equals(Pets anotherPet)
    {
        if (anotherPet == null)
        {
            return false ;
        }
        return ((this.getName().equals(anotherPet.getName())) &&
                (this.getAge() == anotherPet.getAge()) &&
                (this.getWeight() == anotherPet.getWeight())) ;
    }
}

是否可以将其打印在不同的“段落”上？例如，像这样：

Pet Name             Age              Weight
--------------    --------------    -------------- 
Fido                          1               15.0

Tweety                      2                0.1

Sylvester                  10                8.3

Fido                        1               15.0

Dumbo                       6             2000.0

Name: Fido  Age: 1 years   Weight: 15.0 pounds
Name: Tweety  Age: 2 years   Weight: 0.1 pounds
Name: Sylvester  Age: 10 years   Weight: 8.3 pounds
Name: Fido  Age: 1 years   Weight: 15.0 pounds
Name: Dumbo  Age: 6 years   Weight: 2000.0 pounds

List<Pets> petList = new ArrayList<Pets>();
for (int counter = 0; counter < numberOfPets; counter++) 
{
    fileScanner.useDelimiter(",") ;                
    String name = fileScanner.next() ;
    fileScanner.useDelimiter(",") ;
    int age = fileScanner.nextInt() ;
    fileScanner.useDelimiter("[,\\s]") ;
    double weight = fileScanner.nextDouble() ;
    Pets pets = new Pets(name, age, weight) ; 
    sumAge += age ; 
    sumWeight += weight ;
    System.out.printf("%-15s %15d %18s %n", name, age, weight) ; 
    petList.add(pets);
}

for(Pets pet : petList{
    System.out.println(pets.toString()) ;
}

// allows you to store the pets that were entered
Collection<Pets> petsCollection = new ArrayList<>();

// loop and have the user enter pets
for (int i = 0; i < petCount; i++) {
    // your code
    fileScanner.useDelimiter(",") ;                
    String name = fileScanner.next() ;
    fileScanner.useDelimiter(",") ;
    int age = fileScanner.nextInt() ;
    fileScanner.useDelimiter("[,\\s]") ;
    double weight = fileScanner.nextDouble();
    Pets pets = new Pets(name, age, weight); 
    // add to collection
    petsCollection.add(pets);
}

我试图为第二部分创建一个不同的循环，但我遇到了试图访问宠物的问题。唯一可以访问的是最后使用的一个。有什么想法吗

更新：主要问题已经解决，但我还有一个次要问题。当我运行程序时，我得到以下信息：

Name: Fido  Age: 1 years   Weight: 15.0 pounds
Name: 
Tweety  Age: 2 years   Weight: 0.1 pounds
Name: 
Sylvester  Age: 10 years   Weight: 8.3 pounds
Name: 
Fido  Age: 1 years   Weight: 15.0 pounds
Name: 
Dumbo  Age: 6 years   Weight: 2000.0 pounds

---

为什么其余的宠物不与名字对齐？

您在同一个循环中打印两行，因此它们总是在同一段落中

System.out.printf("%-15s %15d %18s %n", name, age, weight) ; 
System.out.println(pets.toString()) ; // Print until above is done

最简单的方法是将宠物存储在一个数组中，然后在完成另一个循环时对其进行迭代

大概是这样的：

Pet Name             Age              Weight
--------------    --------------    -------------- 
Fido                          1               15.0

Tweety                      2                0.1

Sylvester                  10                8.3

Fido                        1               15.0

Dumbo                       6             2000.0

Name: Fido  Age: 1 years   Weight: 15.0 pounds
Name: Tweety  Age: 2 years   Weight: 0.1 pounds
Name: Sylvester  Age: 10 years   Weight: 8.3 pounds
Name: Fido  Age: 1 years   Weight: 15.0 pounds
Name: Dumbo  Age: 6 years   Weight: 2000.0 pounds

List<Pets> petList = new ArrayList<Pets>();
for (int counter = 0; counter < numberOfPets; counter++) 
{
    fileScanner.useDelimiter(",") ;                
    String name = fileScanner.next() ;
    fileScanner.useDelimiter(",") ;
    int age = fileScanner.nextInt() ;
    fileScanner.useDelimiter("[,\\s]") ;
    double weight = fileScanner.nextDouble() ;
    Pets pets = new Pets(name, age, weight) ; 
    sumAge += age ; 
    sumWeight += weight ;
    System.out.printf("%-15s %15d %18s %n", name, age, weight) ; 
    petList.add(pets);
}

for(Pets pet : petList{
    System.out.println(pets.toString()) ;
}

// allows you to store the pets that were entered
Collection<Pets> petsCollection = new ArrayList<>();

// loop and have the user enter pets
for (int i = 0; i < petCount; i++) {
    // your code
    fileScanner.useDelimiter(",") ;                
    String name = fileScanner.next() ;
    fileScanner.useDelimiter(",") ;
    int age = fileScanner.nextInt() ;
    fileScanner.useDelimiter("[,\\s]") ;
    double weight = fileScanner.nextDouble();
    Pets pets = new Pets(name, age, weight); 
    // add to collection
    petsCollection.add(pets);
}

List-petList=new-ArrayList（）；
对于（int counter=0；counter

只需更改

System.out.printf（“%-15s%15d%18s%n”、姓名、年龄、体重）；

进入

List pets=new ArrayList（）；
宠物。添加（新宠物（姓名、年龄、体重））；

---

然后，您可以使用for each循环打印集合。

您可以执行以下操作：

Pet Name             Age              Weight
--------------    --------------    -------------- 
Fido                          1               15.0

Tweety                      2                0.1

Sylvester                  10                8.3

Fido                        1               15.0

Dumbo                       6             2000.0

Name: Fido  Age: 1 years   Weight: 15.0 pounds
Name: Tweety  Age: 2 years   Weight: 0.1 pounds
Name: Sylvester  Age: 10 years   Weight: 8.3 pounds
Name: Fido  Age: 1 years   Weight: 15.0 pounds
Name: Dumbo  Age: 6 years   Weight: 2000.0 pounds

List<Pets> petList = new ArrayList<Pets>();
for (int counter = 0; counter < numberOfPets; counter++) 
{
    fileScanner.useDelimiter(",") ;                
    String name = fileScanner.next() ;
    fileScanner.useDelimiter(",") ;
    int age = fileScanner.nextInt() ;
    fileScanner.useDelimiter("[,\\s]") ;
    double weight = fileScanner.nextDouble() ;
    Pets pets = new Pets(name, age, weight) ; 
    sumAge += age ; 
    sumWeight += weight ;
    System.out.printf("%-15s %15d %18s %n", name, age, weight) ; 
    petList.add(pets);
}

for(Pets pet : petList{
    System.out.println(pets.toString()) ;
}

// allows you to store the pets that were entered
Collection<Pets> petsCollection = new ArrayList<>();

// loop and have the user enter pets
for (int i = 0; i < petCount; i++) {
    // your code
    fileScanner.useDelimiter(",") ;                
    String name = fileScanner.next() ;
    fileScanner.useDelimiter(",") ;
    int age = fileScanner.nextInt() ;
    fileScanner.useDelimiter("[,\\s]") ;
    double weight = fileScanner.nextDouble();
    Pets pets = new Pets(name, age, weight); 
    // add to collection
    petsCollection.add(pets);
}

或者养最小的宠物

int minAge = Integer.MAX_VALUE;
for (Pets pet : petsCollection) {
    minAge = Math.min(minAge, pet.getAge());
}
System.out.printf("The youngest pet is %d%n", minAge);

---

有更优雅的方法可以做到这一点（使用流），但我认为最好是这样开始。

单独存储每只宠物的简单方法是创建一个

ArrayList

就像一个集合，在其中存储每只宠物，并且您可以随时访问它们的信息，知道其中的索引

正如在代码中一样，我们在循环外声明变量，以便在hole类中访问这些变量，然后初始化对象并创建ArrayList（记住在Pets类中创建一个空构造函数）

当您具有读取文件的循环时，您可以使用以下命令将每个宠物添加到ArrayList中：

宠物。添加（新宠物（姓名、年龄、体重））；

因此，在读取循环之外，我们创建了另一个循环来访问ArrayList的每个索引，如果你只想要一只宠物，你可以创建一个循环来找到一个确切的名字或类似的东西，这比只打印和从不存储宠物更有用。因此，基本上你可以使用

pets.get（x）

访问宠物，其中x是宠物的索引

public class PetsMain {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        // We declare variables here
        String name;
        int age;
        double weight;
        Pets pet = new Pets(); // Initialize Object
        ArrayList<Pets> pets = new ArrayList<Pets>(); // We create the ArrayList


        Scanner keyboard = new Scanner(System.in) ;
        System.out.println("Please enter the number of pets") ;
        int numberOfPets = keyboard.nextInt() ;

        String fileName = "pets.txt" ; 
        FileInputStream fileStream = null ;

        String workingDirectory = System.getProperty("user.dir") ;
        System.out.println("Working Directory for this program: " + workingDirectory) ;

        try
        {
            String absolutePath = workingDirectory + "\\" + fileName ;
            System.out.println("Trying to open: " + absolutePath) ;
            fileStream = new FileInputStream(absolutePath) ;
            System.out.println("Opened the file ok.\n") ;
        }
        catch (FileNotFoundException e)
        {
            System.out.println("File \'" + fileName + "\' is missing") ;
            System.out.println("Exiting program. ") ;
            System.exit(0) ;
        }

        Scanner fileScanner = new Scanner(fileStream) ;
        int sumAge = 0 ;
        double sumWeight = 0 ;

        String petName = "Pet Name" ;
        String dogAge = "Age" ;
        String dogWeight = "Weight" ;
        String line = "--------------" ;
        System.out.printf("%11s %15s %19s %n", petName, dogAge, dogWeight) ;
        System.out.printf("%s %17s %17s %n", line, line, line) ;
        for (int counter = 0; counter < numberOfPets; counter++) 
        {
            fileScanner.useDelimiter(",") ;                
            name = fileScanner.next() ;
            fileScanner.useDelimiter(",") ;
            age = fileScanner.nextInt() ;
            fileScanner.useDelimiter("[,\\s]") ;
            weight = fileScanner.nextDouble() ;
            sumAge += age ; 
            sumWeight += weight ;
            System.out.printf("%-15s %15d %18s %n", name, age, weight) ; 

            // **We add the pet to the collection
            pets.add(new Pets(name,age,weight)); // Adding it to the ArrayList
        }

        // Then we acces to the ArrayList and we print what we want.
        for(int x=0; x < pets.size(); x++){
            System.out.print(pets.get(x).toString());
        }

        System.out.println("\nThe total weight is " + sumWeight) ;
        System.out.println("\nThe total age is " + sumAge) ;

        try
        {
            fileStream.close() ;
        }
        catch (IOException e)
        {
            // don't do anything
        }
    }

}

公共类PetsMain{
/**
*@param指定命令行参数
*/
公共静态void main（字符串[]args）{
//我们在这里声明变量
字符串名；
智力年龄；
双倍重量；
宠物宠物=新宠物（）；//初始化对象
ArrayList pets=new ArrayList（）；//我们创建ArrayList
扫描仪键盘=新扫描仪（System.in）；
System.out.println（“请输入宠物数量”）；
int numberOfPets=keyboard.nextInt（）；
字符串fileName=“pets.txt”；
FileInputStream fileStream=null；
字符串workingDirectory=System.getProperty（“user.dir”）；
System.out.println（“此程序的工作目录：“+workingDirectory”）；
尝试
{
字符串absolutePath=workingDirectory+“\\”+文件名；
System.out.println（“试图打开：“+absolutePath”）；
fileStream=新文件输入流（绝对路径）；
System.out.println（“打开文件确定。\n”）；
}
catch（filenotfounde异常）
{
System.out.println（“缺少文件\'”+文件名+“\”）；
System.out.println（“退出程序”）；
系统出口（0）；
}
Scanner fileScanner=新扫描仪（fileStream）；
int sumAge=0；
双倍重量=0；
字符串petName=“Pet Name”；
字符串dogAge=“Age”；
字符串dogWeight=“Weight”；
字符串行=“--------------”；
System.out.printf（“%11s%15s%19s%n”，宠物名，狗龄，狗重）；
System.out.printf（“%s%17s%17s%n”，行，行，行）；
对于（int counter=0；counter

希望它对您有所帮助，如果您有任何问题，请添加评论：）

在这里，您可以轻松找到有关在Arraylist上存储对象的信息并进行打印：

---

你的等号是错误的，你应该覆盖等号（对象o）。什么意思：打印不同的段落？这是命令提示打印，不是文字文档。你应该首先收集输入的宠物（进入

集合

），然后循环打印出来。@Stultuske这就是为什么