How to create an object using a constructor method in Java?

2 years ago
Noah Thompson
1 minute

In Java, we can use constructor methods to create objects. Constructors are special methods that must have the same name as the class and do not have a return type.

The following are the steps to create an object using a constructor method:

  1. Define a class and define a constructor method. The constructor method can have parameters, or it can have no parameters.
public class MyClass {
    private int num;

    // 无参数构造方法
    public MyClass() {
        num = 0;
    }

    // 带参数的构造方法
    public MyClass(int n) {
        num = n;
    }
}
  1. fresh
  2. fresh
  3. fresh
MyClass obj1 = new MyClass();        // 调用无参数构造方法创建对象
MyClass obj2 = new MyClass(10);      // 调用带参数的构造方法创建对象
  1. You can access an object’s properties or call an object’s methods using the object’s name.
int n = obj2.getNum();    // 调用对象的方法
System.out.println(n);    // 打印对象的属性

Important notes:

  1. If a constructor is not defined in a class, Java will automatically provide a default constructor with no parameters.
  2. If a class has a constructor with parameters defined, but does not have a constructor without parameters, then the constructor with parameters must be used when creating an object.
  3. A class can have multiple constructors as long as they differ in the number or type of parameters.

I hope this can help you!

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