Java / Initialization of variables

How can we initialize fields?
There are few ways to do it.

1. Initialization in its declaration - but sometimes we need some logic to do that.
2. Initialization in static block
3. Initialization in block
4. Initialization in constructor
5. Initialization by method

public class MyInitialization 
{
 static int a, b;
 int x, y;
 String name;
 String address;
 
 
 // 1. initialization in its declaration 
 int age = 30;
 
 // 2. initialization in static block 
 static
 {
  a = 7;
  b = 9;  
 }
 
 // 3. initialization in block 
 {
  x = 21;
  y = 23;  
 }
 
 // 4. initialization in constructor 
 MyInitialization()
 {
  this.name = "John";
 }
 
 // 5. initialization by method 
 public void setAddress(String aAddress)
 {
  this.address = aAddress;
 }
 
 public void setX(int aX)
 {
  this.x = aX;
 }

 public static void main(String[] args) 
 {  
  MyInitialization mt = new MyInitialization();
  
  System.out.println( mt.age );  // 1
  
  System.out.println( MyInitialization.a ); // 2
  System.out.println( MyInitialization.b ); // 2
  
  System.out.println( mt.x ); // 3
  System.out.println( mt.y ); // 3
  
  System.out.println( mt.name ); // 4
    
  mt.setAddress("London"); // 5
  System.out.println( mt.address );
 }
}