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Java Programming method concept is important . Method is closely related with the class and object concept. Its important to understand use of merhod within class and object to solve real time problem with java programming. Java Tutor help student to understand the method concept and its implimentation. Following is example with explanation:-
A method is a programmed procedure that is defined as part of a class. A class (and thus an object) can have more than one method.

Syntax of method definition
modifier returnType methodName(parameters) Exception List{
Method Body
}

Method definition composed of six components :

modifiers : like private, public, protected or default. We have already seen private, public and default. Will discuss more about these in the packages section.

ReturnType : The type of the value written by the method. If you don't want to return any value make the return type as void. Return type will be any primitive type or reference type.

MethodName : The name given to the method

parameters: Method is defined with parameters or with out parameters. A method can be defined with any number of parameters.

Exception List: A Method can throw any number of exceptions, will discuss about this on ExceptionHandling section

Method Body: The actual implementation of the method goes here

Example
1. public int sum(int a, int b){
return (a+b);
}

modifier : public
returnType : int
methodName : sum
parameters : a,b
Exception List : none
Method body : calculates the sum of the two parameters and return the sum.

2. void sayHello(){
System.out.println(“Hello”);
}

modifier : default
returnType : void
methodName : sayHello
parameters :none
Exception List : none
Method body : simply prints the message “Hello” to the console.

If no access specifier (modifier) specified to a variable or method, it assumes default access specifier(modifier).

Naming a Method
By convention method names starts with a small character and starting character of subsequent words is capitalized.

Example:
walk()
sleep()
setColor(String s)
getHeight()

Local Variables
Variables declared inside a method are called local variables. These are not accessible out side of the method. You must initialize local variables before using.

Some Points to remember
Trying to use local variables before initializing causes compile time error

Example
class LocalVariable{
int sum(int a, int b){
int c;
System.out.println(c);
return (a+b);
}
}

Since “c” is a local variable, when your program tries to access local variable, before initialization, compiler will throw the error.

For the above program, you will get below error
LocalVariable.java:5: error: variable c might not have been initialized
System.out.println(c);
^
1 error

More About Methods
Methods without returning any value and without parameters
Syntax:
void methodName(){
//body
}

If a method don't return any value, then it's return type must be void

Example
class MethodEx{
void print(){
System.out.println("I am not returning any value");
}

public static void main(String args[]){
MethodEx obj = new MethodEx();
obj.print();
}
}

Output
I am not returning any value

Methods without returning any value and with parameters
Syntax:
void methodName(parameters){
//body
}
You can give any number of parameters to a method

Example
class MethodEx{
void print(int a, int b){
System.out.println("The parameter value is " + a +" " + b);
}
public static void main(String args[]){
MethodEx obj = new MethodEx();
obj.print(10,20);
}
}

Output
The parameter value is 10 20

Methods with returning a value and without parameters
Syntax
returnType methodName(){
//body
}
Here returnType is any primitive or reference type. The method must returns the value which is compatible with the returnType of the method.

Example
class MethodEx{
String fun(){
return "Let's have fun with methods";
}

public static void main(String args[]){
MethodEx obj = new MethodEx();
String s = obj.fun();
System.out.println(s);
}
}

Output
Let's have fun with methods

Observation
The method fun() return type is String, so whatever the value returns by the method fun(), we must store it in the String variable like “String s = obj.fun()”.

Methods with returning a value and with parameters
Syntax
returnType methodName(parameters){
//body
}

A method can have any number of parameters. Here returnType is any primitive or reference type. The method must returns the value which is compatible with the returnType of the method.

Example
class MethodEx{
String fun(String firstName, String lastName, int age){
return "I am " + firstName +" " + lastName + " and my Age is " + age;
}

public static void main(String args[]){
MethodEx obj = new MethodEx();
String s = obj.fun("Aravind", "Phaneendra", 25);
System.out.println(s);
}
}

Output
I am Aravind Phaneendra and my Age is 25

Some Points to Remember
1. returning incompatible value causes the compiler to throw error.
Example
class MethodEx{
int sum(int a, int b){
return 10.01;
}
}

When you try to compile the above program, compiler will throw the below error

MethodEx.java:4: error: possible loss of precision
return 10.01;
^
required: int
found: double
1 error

2. You can call the method in print methods, if it is returning a value, i.e, non void type methods
Example
class MethodEx{
int sum(int a, int b){
return (a+b);
}
public static void main(String args[]){
MethodEx obj = new MethodEx();
System.out.println("Sum of 10 and 20 is " + obj.sum(10,20));
}
}

Output
Sum of 10 and 20 is 30

3. Calling void methods inside the print causes compile time error
Example
class MethodEx{
void print(){
}

public static void main(String args[]){
MethodEx obj = new MethodEx();
System.out.println(obj.print());
}
}

When you try to compile the above program, compiler will throw the below error.
MethodEx.java:7: error: 'void' type not allowed here
System.out.println(obj.print());
^
1 error

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