Difference Between Explicit In Class Initialization And Non Static Instance Initialization

I come from a C++ background and I recently started learning Java from "Thinking in Java" 4th Edition by Bruce Eckel.What's the difference between:

// explicit in class initialization
// saw this on page 126

class A {

}

public class B {
A obj1 = new A();
A obj2 = new A();
}

and

// non static instance initialization
// saw this on page 132

class A {
}
public class B {
A obj1;
A obj2;
{
obj1 = new A();
obj2 = new A();
}
}