INSTANCE VARIABLE IN JAVA WITH EXAMPLE

My assignment is lớn make a program with an instance variable, a string, that should be đầu vào by the user. But I don"t even know what an instance variable is. What is an instance variable?

How bởi vì I create one? What does it do?


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Instance variable is the variable declared inside a class, but outside a method: something like:

class IronMan /** These are all instance variables **/ public String realName; public String<> superPowers; public int age; /** Getters và setters here **/Now this IronMan Class can be instantiated in another class khổng lồ use these variables. Something like:

class Avengers public static void main(String<> a) IronMan ironman = new IronMan(); ironman.realName = "Tony Stark"; // or ironman.setAge(30); This is how we use the instance variables. Shameless plug: This example was pulled from this free e-book here here.


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An instance variable is a variable that is a thành viên of an instance of a class (i.e., associated with something created with a new), whereas a class variable is a thành viên of the class itself.

Every instance of a class will have sầu its own copy of an instance variable, whereas there is only one of each static (or class) variable, associated with the class itself.

What’s the difference between a class variable and an instance variable?

This demo class illustrates the difference:

public class Test public static String classVariable = "I am associated with the class"; public String instanceVariable = "I am associated with the instance"; public void setText(String string) this.instanceVariable = string; public static void setClassText(String string) classVariable = string; public static void main(String<> args) Test test1 = new Test(); Test test2 = new Test(); // Change test1"s instance variable test1.setText("Changed"); System.out.println(test1.instanceVariable); // Prints "Changed" // test2 is unaffected System.out.println(test2.instanceVariable); // Prints "I am associated with the instance" // Change class variable (associated with the class itself) Test.setClassText("Changed class text"); System.out.println(Test.classVariable); // Prints "Changed class text" // Can access static fields through an instance, but there still is only one // (not best practice lớn access static variables through instance) System.out.println(test1.classVariable); // Prints "Changed class text" System.out.println(test2.classVariable); // Prints "Changed class text"