All local variables in a method have default values

Question

Problem:

Hello java programmers,

Myself is a new student in java. I am practicing basic java methods and objects. Finding beginner-level problems and trying to solve them. I recently got a line that says, all local variables in a method have default values. What does it mean? Can you please write a simple code that makes me understand this well?

Thanks guys.

Answer 1

Before everything else, we need to know:

# A local variable is declared in methods, constructors, or blocks.

# A local variable is visible only within the declared method, constructor, or block.

# Access modifiers cannot be used for local variables

See the program below:

public class Gavin {
   public void myAge() {
      int age;
      age = age + 5;
      System.out.println("My age is : " + age);
   }

   public static void main(String args[]) {
      Gavin gavin = new Gavin();
      gavin.myAge();
   }
}

The following program will produce an error because I didn’t initialize the local variable before I use it. So I need to write the program this way:

​public class Gavin {
   public void myAge() {
      int age=20;
      age = age + 5;
      System.out.println("My age is : " + age);
   }
   public static void main(String args[]) {
      Gavin gavin = new Gavin();
      gavin.myAge();
   }
}

Now the program looks perfect and produces the age 25 as an output. I hope things are clear to you now.
Thanks.

Answer 2

First of all, you have to know what is variable?

Variable:

A variable provides us with named storage that our programs can manipulate. Each variable in Java has its own specific type, which determines the size and layout of the memory variable.

There are many kinds of variable but we will discuss local variables.

Local variables:

• Local variables are those variables, declared in methods, constructors, or blocks.
• Local variables are created when the methods, constructors, or blocks are entered and the variables are destroyed when it exits from the method, constructor, or block.
• Access modifiers can not be used for local variables.
• Local variables can only be used with the declared methods, constructors, or blocks.
• The implementation is done at the stack level internally.
• There is no default value for the local variables. So, the local variables should have to declare and an initial value should be assigned before the first use.

Example:

public class LocalVariableTest {

   public void print() {

      int num = 100;

      System.out.println("The number is : " + num);

   }

   public static void main(String args[]) {

      LocalVariableTest obj = new LocalVariableTest();

      obj.print();

   }

}

Output:

The number is: 100

Note:

Local variables can be initialized with a value. If ones try to do this the following error can occur;

“Variable num might not have been initialized.”