The super for loop in C ++ practice and the difference between list and java, listjava

The super for loop in C ++ practice and the difference between list and java, listjava

You can directly modify the attributes of an object in the For loop in Java.

import java.util.ArrayList;import java.util.List;import java.util.regex.*;public class main {    static class Student {        String name;        int id;        public Student(String name, int id) {            this.name = name;            this.id = id;        }        public void setName(String name) {            this.name = name;        }        @Override        public String toString() {            return "Student [name=" + name + ", id=" + id + "]";        }    }    public static void main(String[] args) {        List
 
   mStudents = new ArrayList
  
   ();        mStudents.add(new Student("Tony", 1));        mStudents.add(new Student("Lili", 2));        System.out.println("BEFORE: " + mStudents);        for (Student student : mStudents) {            if (student.id == 1) {                student.setName("zhangsan");            }        }        System.out.println("AFTER: " + mStudents);    }}
  
 

Running result:

BEFORE: [Student [name=Tony, id=1], Student [name=Lili, id=2]]AFTER: [Student [name=zhangsan, id=1], Student [name=Lili, id=2]]

Direct modification in C ++ does not change the object attribute in the List. The result is as follows:

        for (Student student : mStudents) {            if (student.id == 1) {                student.setName("zhangsan");            }        }

To achieve the effect of java, you need to add an address character:

        for (Student &student : mStudents) {            if (student.id == 1) {                student.setName("zhangsan");            }        }

Because C ++ focuses on value transfer and address transfer. This distinction is not made in java, but it is a transfer address. Therefore, the sub-function can directly modify the attribute values of the passed objects. In C ++, you need to add the & get address character to convert it into a transfer address.