如何在Java中使用Person數組中的循環尋找最老的人

Question

我是編程新手我需要編寫一個代碼來查找Person Array中最老的人。請幫忙。該程序已編譯但未執行。它給了我只有陣列的大小，但不是最老的人。我將不勝感激任何幫助。 我的代碼是波紋管：

import java.util.ArrayList; 
public class PersonCollection { 
public static void main(String[] args) { 
    ArrayList<Person> aList = new ArrayList<Person>(); 
    // Create 5 new Person objects and output their data 
    Person person1 = new Person("Diana", "Rockman", 38, 'F', "603-28-5324"); 
    Person person2 = new Person("Arthur","Montgamery", 49, 'M',"402-23-5463"); 
    Person person3 = new Person("Kim", "Balcer", 35, 'F',"607-34-5463"); 
    Person person4 = new Person("Ghaffar","Kucher", 36, 'M',"537-52-6324"); 
    Person person5 = new Person("Zach","Boot", 19, 'M', "732-65-7364"); 
    aList.add(person1); 
    aList.add(person2); 
    aList.add(person3); 
    aList.add(person4); 
    aList.add(person5); 
    System.out.println("The size of the list is:" + aList.size()); 
} 
public static void oldestPerson(String[] names, int[] ages) 
    { 
     int index = 0; 
     int oldest = ages[0]; 
     for (int i=0; i < ages.length; i++) 
     { 

      if(ages[i] > oldest) 
      {index = i; 
       oldest = ages[i]; 
      } 

      System.out.println("Person" + names[index] + "is the oldest:" +  ages [index]); 
} 
} 
} 

Answer 1

你是不是調用oldestPerson方法的任何地方（最好稱之爲findOldestPerson）。此外，您應該設計該方法，以List<Person>作爲參數。

這可能幫助：

public static void findOldestPerson(List<Person> persons) { 
    Person oldest = null; 
    for (Person p : persons) { 
     if (oldest == null || p.getAge() > oldest.getAge()) oldest = p; 
    } 
    // Do something with the oldest person. 
} 

Answer 2

後System.out.println("The size of the list is:" + aList.size());

你必須添加一個調用你的oldestPerson方法，你可以用這種方式更新方法：

public static void oldestPerson(ArrayList<Person> aList) 
    { 
     Person oldest = new Person(); 
     for (Person p : aList) 
     { 

      if(p.getAge() > oldest.getAge()) 
      { 
       oldest = p; 
      } 

      System.out.println("Person" + p.getName() + "is the oldest:" + p.getAge()); 
} 

我用一個getter方法，因爲我認爲屬性關於Person類是private，但如果是public，你可以這樣做：p.age或p.name ..

Answer 3

與Java 8 ...

public class PersonTest { 
    public static class Person { 
     public String first; 
     public String last; 
     public int age; 
     public char gender; 
     public String ssn; 

     public Person(String first, String last, int age, char gender, String ssn) { 
      this.first = first; 
      this.last = last; 
      this.age = age; 
      this.gender = gender; 
      this.ssn = ssn; 
     } 
    } 

    public static void main(String[] args) { 
     List<Person> aList = Arrays.asList(
       new Person("Diana", "Rockman", 38, 'F', "603-28-5324"), 
       new Person("Arthur","Montgamery", 49, 'M',"402-23-5463"), 
       new Person("Kim", "Balcer", 35, 'F',"607-34-5463"), 
       new Person("Ghaffar","Kucher", 36, 'M',"537-52-6324"), 
       new Person("Zach","Boot", 19, 'M', "732-65-7364")); 

     Person oldest = aList.stream().max((a,b) -> a.age - b.age).get(); 
     System.out.println(String.format("The oldest person is %s %s", oldest.first, oldest.last)); 
    } 

}