JAVA: Classes and Objects - Revision history

Unknown user: /* Membuat multiple Object dengan hanya satu type saja (good practice) */

2022-04-30T08:39:18Z

Membuat multiple Object dengan hanya satu type saja (good practice)

← Older revision		Revision as of 08:39, 30 April 2022
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	===Membuat multiple Object dengan hanya satu type saja (good practice)===		===Membuat multiple Object dengan hanya satu type saja (good practice)===

	In real-time, ~~we need different objects of a class in different methods~~. ~~Creating a number of references for storing them is not a good practice and therefore we declare a static reference variable and use it whenever required~~. ~~In this case~~, ~~wastage of memory is less~~. ~~The objects that are not referenced anymore will be destroyed by~~ Garbage Collector ~~of java~~. ~~Example~~:		Pada real-time, kita membutuhkan beberapa Object dari sebuah Class di method yang berbeda. Membuat sejumlah referensi untuk menyimpannya bukanlah praktik yang baik dan oleh karena itu kita mendeklarasikan variabel referensi statis dan menggunakannya kapan pun diperlukan. Dalam hal ini, pemborosan memori lebih sedikit. Object yang tidak direferensikan lagi akan dimusnahkan oleh java Garbage Collector. Contoh:

	Test test = new Test();		Test test = new Test();
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	In inheritance system, we use parent class reference variable to store a sub-class object. In this case, we can switch into different subclass objects using same referenced variable. Example:		In inheritance system, we use parent class reference variable to store a sub-class object. In this case, we can switch into different subclass objects using same referenced variable. Example:

			Dalam sistem inheritance, kami menggunakan variabel referensi parent Class untuk menyimpan object sub-class. Dalam hal ini, kita dapat beralih ke object subclass yang berbeda menggunakan variabel referensi yang sama. Contoh:

	class Animal {}		class Animal {}

Unknown user: /* Creating multiple objects by one type only (A good practice) */

2022-04-30T08:34:57Z

Creating multiple objects by one type only (A good practice)

← Older revision		Revision as of 08:34, 30 April 2022
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	Object obj = in.readObject();		Object obj = in.readObject();

	===~~Creating~~ multiple ~~objects by one~~ type ~~only~~ (A good practice)===		===Membuat multiple Object dengan hanya satu type saja (good practice)===

	In real-time, we need different objects of a class in different methods. Creating a number of references for storing them is not a good practice and therefore we declare a static reference variable and use it whenever required. In this case, wastage of memory is less. The objects that are not referenced anymore will be destroyed by Garbage Collector of java. Example:		In real-time, we need different objects of a class in different methods. Creating a number of references for storing them is not a good practice and therefore we declare a static reference variable and use it whenever required. In this case, wastage of memory is less. The objects that are not referenced anymore will be destroyed by Garbage Collector of java. Example:

Unknown user: /* Anonymous objects */

2022-04-30T08:34:08Z

Anonymous objects

← Older revision		Revision as of 08:34, 30 April 2022
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	}		}

	==Anonymous objects==		===Anonymous objects===

	Anonymous objects are the objects that are instantiated but are not stored in a reference variable.		Anonymous objects are the objects that are instantiated but are not stored in a reference variable.
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	}		}
	});		});




	==Referensi==		==Referensi==

	* https://www.geeksforgeeks.org/classes-objects-java/		* https://www.geeksforgeeks.org/classes-objects-java/

Unknown user: /* Cara membuat Object dari sebuah Class */

2022-04-30T08:33:35Z

Cara membuat Object dari sebuah Class

← Older revision		Revision as of 08:33, 30 April 2022
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	'''Menggunakan Class.forName(String className) method:''''		'''Menggunakan Class.forName(String className) method:''''
	There is a pre-defined class in java.lang package with name Class. The forName(String className) method returns the Class object associated with the class with the given string name.We have to give the fully qualified name for a class. On calling new Instance() method on this Class object returns new instance of the class with the given string name.		There is a pre-defined class in java.lang package with name Class. The forName(String className) method returns the Class object associated with the class with the given string name.We have to give the fully qualified name for a class. On calling new Instance() method on this Class object returns new instance of the class with the given string name.


			Ada Class yang telah ditentukan sebelumnya dalam paket java.lang dengan nama Class. Metode forName(String className) mengembalikan object Class yang terkait dengan Class dengan nama string yang diberikan. Kita harus memberikan nama yang sepenuhnya memenuhi syarat untuk sebuah Class. Saat memanggil method Instance() baru pada object Class ini mengembalikan instance baru dari Class dengan nama string yang diberikan.

	// creating object of public class Test		// creating object of public class Test
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	'''Menggunakan clone() method:''''		'''Menggunakan clone() method:''''
	clone() method ~~is present in~~ Object class. ~~It creates and returns a~~ copy ~~of the object~~.		clone() method merepresentasikan Object class. Ini akan membuat dan mengembalikan sebuah copy dari Object.

	// creating object of class Test		// creating object of class Test
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	'''Deserialization:'''		'''Deserialization:'''
	De-serialization ~~is technique of reading an object from the~~ saved state ~~in a~~ file. ~~Refer~~ Serialization/De-Serialization in java		De-serialization adalah teknik untuk membaca sebuah Object dari saved state di sebuah file. Mereferensi pada Serialization/De-Serialization di java

	FileInputStream file = new FileInputStream(filename);		FileInputStream file = new FileInputStream(filename);

Unknown user: /* Initialisasi sebuah Object */

2022-04-30T08:24:46Z

Initialisasi sebuah Object

← Older revision		Revision as of 08:24, 30 April 2022
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			===Cara membuat Object dari sebuah Class===

	~~Ways to create object of a class~~		Ada empat cara untuk membuat Object di Java. Sebenarnya hanya ada satu cara (dengan menggunakan keyword baru), dan sisanya secara internal menggunakan keyword baru.
	~~There are four ways to create objects in java~~.~~Strictly speaking there is only one way~~(~~by using new~~ keyword),~~and the rest internally use new~~ keyword.

	~~Using new~~ keyword: ~~It is the most common and general way to create object in java~~. ~~Example~~:		'''Menggunakan keyword baru:'''
			Ini merupakan cara yang paling banyak digunakan dalam membuat Object di Java. Contoh:

	// creating object of class Test		// creating object of class Test
	Test t = new Test();		Test t = new Test();

	~~Using~~ Class.forName(String className) method: There is a pre-defined class in java.lang package with name Class. The forName(String className) method returns the Class object associated with the class with the given string name.We have to give the fully qualified name for a class. On calling new Instance() method on this Class object returns new instance of the class with the given string name.		'''Menggunakan Class.forName(String className) method:''''
			There is a pre-defined class in java.lang package with name Class. The forName(String className) method returns the Class object associated with the class with the given string name.We have to give the fully qualified name for a class. On calling new Instance() method on this Class object returns new instance of the class with the given string name.

	// creating object of public class Test		// creating object of public class Test
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	Test obj = (Test)Class.forName("com.p1.Test").newInstance();		Test obj = (Test)Class.forName("com.p1.Test").newInstance();

	~~Using~~ clone() method: clone() method is present in Object class. It creates and returns a copy of the object.		'''Menggunakan clone() method:''''
			clone() method is present in Object class. It creates and returns a copy of the object.

	// creating object of class Test		// creating object of class Test
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	Test t2 = (Test)t1.clone();		Test t2 = (Test)t1.clone();

	Deserialization: De-serialization is technique of reading an object from the saved state in a file. Refer Serialization/De-Serialization in java		'''Deserialization:'''
			De-serialization is technique of reading an object from the saved state in a file. Refer Serialization/De-Serialization in java

	FileInputStream file = new FileInputStream(filename);		FileInputStream file = new FileInputStream(filename);
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	Object obj = in.readObject();		Object obj = in.readObject();

	Creating multiple objects by one type only (A good practice)		===Creating multiple objects by one type only (A good practice)===

	In real-time, we need different objects of a class in different methods. Creating a number of references for storing them is not a good practice and therefore we declare a static reference variable and use it whenever required. In this case, wastage of memory is less. The objects that are not referenced anymore will be destroyed by Garbage Collector of java. Example:		In real-time, we need different objects of a class in different methods. Creating a number of references for storing them is not a good practice and therefore we declare a static reference variable and use it whenever required. In this case, wastage of memory is less. The objects that are not referenced anymore will be destroyed by Garbage Collector of java. Example:

Unknown user: /* Initialisasi sebuah Object */

2022-04-30T07:53:26Z

Initialisasi sebuah Object

← Older revision		Revision as of 07:53, 30 April 2022
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	Operator baru membuat instance Class dengan mengalokasikan memori untuk object baru dan mengembalikan referensi ke memori tersebut. Operator baru juga memanggil constructor class.		Operator baru membuat instance Class dengan mengalokasikan memori untuk object baru dan mengembalikan referensi ke memori tersebut. Operator baru juga memanggil constructor class.


	// Class Declaration		// Class Declaration
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	Hi my name is tuffy.		Hi my name is tuffy.
	My breed,age and color are papillon,5,white		My breed,age and color are papillon,5,white

	This class contains a single constructor. We can recognize a constructor because its declaration uses the same name as the class and it has no return type. The Java compiler differentiates the constructors based on the number and the type of the arguments. The constructor in the Dog class takes four arguments. The following statement provides “tuffy”,”papillon”,5,”white” as values for those arguments:

	Class ini berisi satu constructor. Kita dapat mengenali constructor karena deklarasinya menggunakan nama yang sama dengan kelasnya dan tidak memiliki tipe return. Compiler Java membedakan constructor berdasarkan jumlah dan tipe argumen. Construktor di Dog Class membutuhkan empat argumen. Pernyataan berikut memberikan "tuffy", "papillon", 5, "putih" sebagai nilai untuk argumen tersebut:		Class ini berisi satu constructor. Kita dapat mengenali constructor karena deklarasinya menggunakan nama yang sama dengan kelasnya dan tidak memiliki tipe return. Compiler Java membedakan constructor berdasarkan jumlah dan tipe argumen. Construktor di Dog Class membutuhkan empat argumen. Pernyataan berikut memberikan "tuffy", "papillon", 5, "putih" sebagai nilai untuk argumen tersebut:
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	[[File:Dog-constructor.png\|center\|200px\|thumb]]		[[File:Dog-constructor.png\|center\|200px\|thumb]]

	~~Note~~ : ~~All classes have at least one~~ constructor. ~~If a class does not explicitly declare any~~, ~~the~~ Java ~~compiler automatically provides a no-argument~~ constructor, ~~also called the~~ default ~~constructor~~. ~~This~~ default constructor ~~calls the class parent’s no-argument constructor~~ (~~as it contain only one statement i.e~~ super();), ~~or the~~ Object class ~~constructor if the class has no other~~ parent (as Object ~~class is~~ parent ~~of all classes either directly or indirectly~~).		Catatan: Semua Class memiliki setidaknya satu constructor. Jika sebuah Class tidak secara eksplisit mendeklarasikan apapun, compiler Java secara otomatis menyediakan constructor tanpa argumen, juga disebut constructor default. Constructor default ini memanggil constructor tanpa argumen parent Class (karena hanya berisi satu pernyataan yaitu super();), atau constructor class Object jika class tidak memiliki parent lain (karena class Object adalah parent dari semua Class baik secara langsung maupun tidak langsung ).




	Ways to create object of a class		Ways to create object of a class
	There are four ways to create objects in java.Strictly speaking there is only one way(by using new keyword),and the rest internally use new keyword.		There are four ways to create objects in java.Strictly speaking there is only one way(by using new keyword),and the rest internally use new keyword.

Unknown user: /* Initialisasi sebuah Object */

2022-04-30T07:49:59Z

Initialisasi sebuah Object

← Older revision		Revision as of 07:49, 30 April 2022
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	This class contains a single constructor. We can recognize a constructor because its declaration uses the same name as the class and it has no return type. The Java compiler differentiates the constructors based on the number and the type of the arguments. The constructor in the Dog class takes four arguments. The following statement provides “tuffy”,”papillon”,5,”white” as values for those arguments:		This class contains a single constructor. We can recognize a constructor because its declaration uses the same name as the class and it has no return type. The Java compiler differentiates the constructors based on the number and the type of the arguments. The constructor in the Dog class takes four arguments. The following statement provides “tuffy”,”papillon”,5,”white” as values for those arguments:

	Class ini berisi satu constructor. Kita dapat mengenali constructor karena deklarasinya menggunakan nama yang sama dengan kelasnya dan tidak memiliki tipe ~~pengembalian~~. ~~Kompiler~~ Java membedakan ~~konstruktor~~ berdasarkan jumlah dan ~~jenis~~ argumen. ~~Konstruktor~~ di ~~kelas Anjing~~ membutuhkan empat argumen. Pernyataan berikut memberikan "tuffy", "papillon", 5, "putih" sebagai nilai untuk argumen tersebut:		Class ini berisi satu constructor. Kita dapat mengenali constructor karena deklarasinya menggunakan nama yang sama dengan kelasnya dan tidak memiliki tipe return. Compiler Java membedakan constructor berdasarkan jumlah dan tipe argumen. Construktor di Dog Class membutuhkan empat argumen. Pernyataan berikut memberikan "tuffy", "papillon", 5, "putih" sebagai nilai untuk argumen tersebut:

			Dog tuffy = new Dog("tuffy","papillon",5, "white");

			Hasil menjalankan perintah tersebut dapat di gambarkan sebagai:

	Dog ~~tuffy = new Dog("tuffy","papillon",5, "white");~~		[[File:Dog-constructor.png\|center\|200px\|thumb]]

	~~The result of executing this statement can be illustrated as :~~
	~~Untitled~~

	Note : All classes have at least one constructor. If a class does not explicitly declare any, the Java compiler automatically provides a no-argument constructor, also called the default constructor. This default constructor calls the class parent’s no-argument constructor (as it contain only one statement i.e super();), or the Object class constructor if the class has no other parent (as Object class is parent of all classes either directly or indirectly).		Note : All classes have at least one constructor. If a class does not explicitly declare any, the Java compiler automatically provides a no-argument constructor, also called the default constructor. This default constructor calls the class parent’s no-argument constructor (as it contain only one statement i.e super();), or the Object class constructor if the class has no other parent (as Object class is parent of all classes either directly or indirectly).

Unknown user: /* Initialisasi sebuah Object */

2022-04-30T07:30:45Z

Initialisasi sebuah Object

← Older revision		Revision as of 07:30, 30 April 2022
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	Output:		Output:

	Hi my name is tuffy.		Hi my name is tuffy.
	My breed,age and color are papillon,5,white		My breed,age and color are papillon,5,white

	This class contains a single constructor. We can recognize a constructor because its declaration uses the same name as the class and it has no return type. The Java compiler differentiates the constructors based on the number and the type of the arguments. The constructor in the Dog class takes four arguments. The following statement provides “tuffy”,”papillon”,5,”white” as values for those arguments:		This class contains a single constructor. We can recognize a constructor because its declaration uses the same name as the class and it has no return type. The Java compiler differentiates the constructors based on the number and the type of the arguments. The constructor in the Dog class takes four arguments. The following statement provides “tuffy”,”papillon”,5,”white” as values for those arguments:
	Dog tuffy = new Dog("tuffy","papillon",5, "white");
			Class ini berisi satu constructor. Kita dapat mengenali constructor karena deklarasinya menggunakan nama yang sama dengan kelasnya dan tidak memiliki tipe pengembalian. Kompiler Java membedakan konstruktor berdasarkan jumlah dan jenis argumen. Konstruktor di kelas Anjing membutuhkan empat argumen. Pernyataan berikut memberikan "tuffy", "papillon", 5, "putih" sebagai nilai untuk argumen tersebut:



			Dog tuffy = new Dog("tuffy","papillon",5, "white");

	The result of executing this statement can be illustrated as :		The result of executing this statement can be illustrated as :
	Untitled		Untitled

Unknown user: /* Initialisasi sebuah Object */

2022-04-30T07:26:21Z

Initialisasi sebuah Object

← Older revision		Revision as of 07:26, 30 April 2022
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	==Initialisasi sebuah Object==		==Initialisasi sebuah Object==

	~~The new operator instantiates a class by allocating memory for a new object and returning a reference to that memory. The new operator also invokes the class constructor.~~

	Operator baru membuat instance Class dengan mengalokasikan memori untuk object baru dan mengembalikan referensi ke memori tersebut. Operator baru juga memanggil constructor class.		Operator baru membuat instance Class dengan mengalokasikan memori untuk object baru dan mengembalikan referensi ke memori tersebut. Operator baru juga memanggil constructor class.

Unknown user: /* Initializing an object */

2022-04-30T07:22:01Z

Initializing an object

← Older revision		Revision as of 07:22, 30 April 2022
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	Jika kita mendeklarasikan variabel referensi(tuffy) seperti di atas, nilainya tidak akan ditentukan (null) sampai sebuah object benar-benar dibuat dan ditugaskan padanya. Cukup mendeklarasikan variabel referensi tidak membuat object.		Jika kita mendeklarasikan variabel referensi(tuffy) seperti di atas, nilainya tidak akan ditentukan (null) sampai sebuah object benar-benar dibuat dan ditugaskan padanya. Cukup mendeklarasikan variabel referensi tidak membuat object.

	==~~Initializing an object~~==		==Initialisasi sebuah Object==

	The new operator instantiates a class by allocating memory for a new object and returning a reference to that memory. The new operator also invokes the class constructor.		The new operator instantiates a class by allocating memory for a new object and returning a reference to that memory. The new operator also invokes the class constructor.

			Operator baru membuat instance Class dengan mengalokasikan memori untuk object baru dan mengembalikan referensi ke memori tersebut. Operator baru juga memanggil constructor class.


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	// using Cat object		// using Cat object
	obj = new Cat();		obj = new Cat();
	}		}


	==Anonymous objects==		==Anonymous objects==