What is the difference between fields and properties in a java class

For example, suppose you want to create a number of Bicycle objects and assign each a serial number, beginning with 1 for the first object. This ID number is unique to each object and is therefore an instance variable.

At the same time, you need a field to keep track of how many Bicycle objects have been created so that you know what ID to assign to the next one. Such a field is not related to any individual object, but to the class as a whole. For this you need a class variable, numberOfBicycles , as follows:. You can use the Bicycle constructor to set the id instance variable and increment the numberOfBicycles class variable:.

The Java programming language supports static methods as well as static variables. Static methods, which have the static modifier in their declarations, should be invoked with the class name, without the need for creating an instance of the class, as in. A common use for static methods is to access static fields. For example, we could add a static method to the Bicycle class to access the numberOfBicycles static field:. The static modifier, in combination with the final modifier, is also used to define constants.

The final modifier indicates that the value of this field cannot change. Mostly for class internal use. Properties can be changed by setter and they are exposed by getters. Similarly using fields , [In hibernate it is the recommended way to MAP using fields, where private int id; is annotated Id, but with Property you have more control]. Java doc says: Field is a data member of a class.

A field is non static, non-transient instance variable. In conclusion, the key distinction between variables is whether they are fields or non-fields, meaning whether they are inside a methods or outside all methods. A variable is the name given to a memory location. It is the basic unit of storage in a program. A field is a data member of a class. Unless specified otherwise, a field can be public, static, not static and final. An attribute is another term for a field. A property is a term used for fields, but it typically has getter and setter combination.

Actually these two terms are often used to represent same thing, but there are some exceptional situations. A field can store the state of an object. Also all fields are variables. So it is clear that there can be variables which are not fields. So looking into the 4 type of variables class variable, instance variable, local variable and parameter variable we can see that class variables and instance variables can affect the state of an object.

In other words if a class or instance variable changes,the state of object changes. So we can say that class variables and instance variables are fields while local variables and parameter variables are not. The question is old but another important difference between a variable and a field is that a field gets a default value when it's declared.

A variable, on the other hand, must be initialized. A variable is something that you declare, which can by default change and have different values, but that can also be explicitly said to be final. In Java that would be:. So basically, a variable is anything that is declared and can hold values. Method foo above returns a variable for example.. It returns a variable of type Integer which holds the memory address of the new Integer ; Everything else you see above are also variables, listVariable, aFinalVariableExample and explained here:.

A field is a variable where scope is more clear or concrete. The variable returning from method foo 's scope is not clear in the example above, so I would not call it a field.

On the other hand, iAmAlsoVariable is a "local" field, limited by the scope of the method foo, and listVariable is an "instance" field where the scope of the field variable is limited by the objects scope. I do not know about attribute and I would also like to repeat that this is my understanding of what variables, fields and properties are. It is a variable inside a class class variable or instance variable. Object operates by attributes which define a set of characteristics.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Ask Question. Asked 9 years, 7 months ago. Active 8 months ago. Viewed k times. Improve this question. Victor Lyuboslavsky Victor Lyuboslavsky 9, 23 23 gold badges 79 79 silver badges bronze badges. The final keyword is called a "modifier". You will learn more about these in the Java Modifiers Chapter. If you create multiple objects of one class, you can change the attribute values in one object, without affecting the attribute values in the other:.

Change the value of x to 25 in myObj2 , and leave x in myObj1 unchanged:. We just launched W3Schools videos. Get certified by completing a course today! If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail:.

The next chapter will teach you how to create class methods and how to access them with objects. Report Error.