java中非静态变量的静态初始化器块与常规初始化有什么区别

Question

初始化的区别是什么：1）int i=47；或2）int i；{i=47；在哪些情况下我们需要第一个或第二个？

public class Bath {
  private String // Initializing at point of definition:
    s1 = "Happy",
    s2 = "Happy",
    s3, s4;
  private Soap castile;
  int i;
  private float toy;
  public Bath() {
    System.out.println("Inside Bath()");
    s3 = "Joy";
    toy = 3.14f;
    castile = new Soap();
  }
  // Instance initialization:
  { i = 47; }
 }

Answer 1

实例初始化允许您在最终为实例变量赋值之前进行一些预先计算。例如：

public class Bath {
  private String // Initializing at point of definition:
    s1 = "Happy",
    s2 = "Happy",
    s3, s4;
  private Soap castile;
  int i;
  private float toy;

  public Bath() {
    System.out.println("Inside Bath()");
    s3 = "Joy";
    toy = 3.14f;
    castile = new Soap();
  }

  // Instance initialization:
  { 
    // some pre-calculations
    int sum = 2*3 + 5*5 + 5;
    int sum2 = 2*4 + 3;
    for(int i=0; i<5; i++) {
      sum2 += i;
    }

    // assign
    i = sum + sum2; 
  }
 }