Get value method java

Field get() method in Java with Examples

The get() method of java.lang.reflect.Field used to get the value of the field object. If Field has a primitive type then the value of the field is automatically wrapped in an object. If the field is a static field, the argument of obj is ignored; it may be null Otherwise, the underlying field is an instance field. This method throws a NullPointerException if the specified obj argument is null and an IllegalArgumentException If the specified object is not an instance of the class or interface declaring the underlying field. If the field is hidden in the type of obj, the field’s value is obtained according to the preceding rules. Syntax:

public double get(Object obj) throws IllegalArgumentException, IllegalAccessException

Parameters: This method accepts a single parameter obj which is the object to extract the field value from. Return value: This method returns the value of the represented field in object obj; primitive values are wrapped in an appropriate object before being returned. Exception: This method throws following Exception:

1. IllegalAccessException– if this Field object is enforcing Java language access control and the underlying field is inaccessible.
2. IllegalArgumentException– if the specified object is not an instance of the class or interface declaring the underlying field (or a subclass or implementer thereof).
3. NullPointerException– if the specified object is null and the field is an instance field.
4. ExceptionInInitializerError– if the initialization provoked by this method fails.

Below programs illustrate get() method: Program 1:

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Returning a Value from a Method

You declare a method’s return type in its method declaration. Within the body of the method, you use the return statement to return the value.

Any method declared void doesn’t return a value. It does not need to contain a return statement, but it may do so. In such a case, a return statement can be used to branch out of a control flow block and exit the method and is simply used like this:

If you try to return a value from a method that is declared void , you will get a compiler error.

Any method that is not declared void must contain a return statement with a corresponding return value, like this:

The data type of the return value must match the method’s declared return type; you can’t return an integer value from a method declared to return a boolean.

The getArea() method in the Rectangle Rectangle class that was discussed in the sections on objects returns an integer:

// a method for computing the area of the rectangle public int getArea()

This method returns the integer that the expression width*height evaluates to.

The getArea method returns a primitive type. A method can also return a reference type. For example, in a program to manipulate Bicycle objects, we might have a method like this:

public Bicycle seeWhosFastest(Bicycle myBike, Bicycle yourBike, Environment env) < Bicycle fastest; // code to calculate which bike is // faster, given each bike's gear // and cadence and given the // environment (terrain and wind) return fastest; >

Returning a Class or Interface

If this section confuses you, skip it and return to it after you have finished the lesson on interfaces and inheritance.

When a method uses a class name as its return type, such as whosFastest does, the class of the type of the returned object must be either a subclass of, or the exact class of, the return type. Suppose that you have a class hierarchy in which ImaginaryNumber is a subclass of java.lang.Number , which is in turn a subclass of Object , as illustrated in the following figure .

The class hierarchy for ImaginaryNumber

Now suppose that you have a method declared to return a Number :

public Number returnANumber()

The returnANumber method can return an ImaginaryNumber but not an Object . ImaginaryNumber is a Number because it’s a subclass of Number . However, an Object is not necessarily a Number — it could be a String or another type.

You can override a method and define it to return a subclass of the original method, like this:

public ImaginaryNumber returnANumber()

This technique, called covariant return type, means that the return type is allowed to vary in the same direction as the subclass.

Note: You also can use interface names as return types. In this case, the object returned must implement the specified interface.

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Getting a Value from a Method in Java

The things in parentheses are parameters. Each time you call your goToTheSupermarketAndBuySome method, you put a different value in the method’s parameter list.

Now what happens when your friend returns from the supermarket? “Here’s the bread you asked me to buy,” says your friend. As a result of carrying out your wishes, your friend returns something to you. You made a method call, and the method returns information (or better yet, the method returns some food).

The thing returned to you is called the method’s return value, and the type of thing returned to you is called the method’s return type.

A Java example

This code shows a method that returns a value

import static java.lang.System.out;

double getInterest(double rate)

public class methodReturn   public static void main(String[] args)  System.out.println(returnNumber());  System.out.println(returnLetter());  System.out.println(returnDouble());  System.out.println(addNumbers(3,3));  >  public static int returnNumber()  return(4);  >  public static char returnLetter()  return('g');  >  public static double returnDouble()  return(10.5);  >  public static int addNumbers(int num1, int num2)  int sum = num1 + num2;  return(sum);  > >