| 5. 20. 1. 创建对象 |
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- Using the new keyword.
- new is always followed by the constructor of the class.
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For example, to create an Employee object, you write: |
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Employee employee = new Employee();
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Here, 'employee' is an object reference of type Employee. |
- Once you have an object, you can call its methods and access its fields, by using the object reference.
- You use a period (.) to call a method or a field.
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For example: |
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objectReference.methodName
objectReference.fieldName
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The following code, for instance, creates an Employee object and assigns values to its age and salary fields: |
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public class MainClass {
public static void main(String[] args) {
Employee employee = new Employee();
employee.age = 24;
employee.salary = 50000;
}
}
class Employee {
public int age;
public double salary;
public Employee() {
}
public Employee(int ageValue, double salaryValue) {
age = ageValue;
salary = salaryValue;
}
}
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When an object is created, the JVM also performs initialization that assign default values to fields. |