Java java.lang.reflect.Constructor用法及代碼示例

// Java program to show uses of Constructor class
// present in java.lang.reflect package
// Importing package to that examine and
// introspect upon itself
import java.lang.reflect.*;
// Class 1
// Helper class
class Employee {
    // Member variables of this class
    int empno;
    String name;
    String address;
    // Constructor of this class
    // Constructor 1
    public Employee(int empno, String name, String address)
    {
        // 'this' keyword refers to the
        // current object itself
        this.empno = empno;
        this.name = name;
        this.address = address;
    }
    // Constructor 2
    public Employee(int empno, String name)
    {
        this.empno = empno;
        this.name = name;
    }
    // Constructor 3
    private Employee(String address)
    {
        this.address = address;
    }
    // Constructor 4
    protected Employee(int empno) { this.empno = empno; }
}
// Class 2
// Main class
public class GFG {
    // Main driver method
    public static void main(String args[])
    {
        // Creating an object of above class
        // in the main() method
        Class c = Employee.class;
        // Display message
        System.out.println("All public constructor are :");
        Constructor[] cons = c.getConstructors();
        for (Constructor con : cons)
            // It will return all public constructor
            System.out.print(con.getName() + " ");
        // Display message for better readability
        System.out.println(
            "\n\nAll  constructor irrespective of access modifiers");
        // Getting constructors of this class
        // using getDeclaredConstructors() method
        cons = c.getDeclaredConstructors();
        // Iterating to print all constructors
        for (Constructor con : cons)
            System.out.print(con.getName() + " ");
        // Display message
        System.out.println(
            "\n\naccess modifiers of each constructor");
        // Iterating to get all the access modifiers
        for (Constructor con : cons)
            // Print all the access modifiers for all
            // constructors
            System.out.print(
                Modifier.toString(con.getModifiers())
                + " ");
        // Parameters types
        // Display message only
        System.out.println(
            "\n\ngetting parameters type of each constructor");
        // Iterating to get parameter types of each
        // constructor using for-each loop
        for (Constructor con : cons) {
            Class[] parameratertypes
                = con.getParameterTypes();
            for (Class c1 : parameratertypes) {
                // Print and display parameter types of all
                // constructors
                System.out.print(c1.getName() + " ");
            }
            // Here we are done with inner loop
            // New line
            System.out.println();
        }
    }
}