初始化_03

标签：java   对象   类   

类中域为基本类型可以被自动初始化为0，对象引用会被初始化为null。

初始化对象引用的方法

{

1.在定义对象的地方。

2.在类的构造器中

3.在正要使用对象之前（惰性初始化）

4.实例初始化

}

class Soap {
  private String s;
  Soap() {
    print("Soap()");
    s = "Constructed";//2<span style="font-size:14px;">在类的构造器中</span>
  }
  public String toString() { return s; }
}	

public class Bath {
  private String // 1<span style="font-size:14px;">在定义对象的地方</span>
    s1 = "Happy",
    s2 = "Happy",
    s3, s4;
  private Soap castille;
  private int i;
  private float toy;
  public Bath() {
    print("Inside Bath()");
    s3 = "Joy";
    toy = 3.14f;
    castille = new Soap();//<span style="font-size:14px;">4实例初始化</span>
  }	
  // Instance initialization:
  { i = 47; }
  public String toString() {
    if(s4 == null) // Delayed initialization:
      s4 = "Joy";
    return
      "s1 = " + s1 + "\n" +
      "s2 = " + s2 + "\n" +
      "s3 = " + s3 + "\n" +
      "s4 = " + s4 + "\n" +
      "i = " + i + "\n" +
      "toy = " + toy + "\n" +
      "castille = " + castille;
  }	
  public static void main(String[] args) {
    Bath b = new Bath();//<span style="font-size:14px;">3在正要使用对象之前（惰性初始化）</span>
    print(b);
  }
} /* Output:
Inside Bath()
Soap()
s1 = Happy
s2 = Happy
s3 = Joy
s4 = Joy
i = 47
toy = 3.14
castille = Constructed

初始化_03

标签：java   对象   类   

原文地址：http://blog.csdn.net/chaoshenyutou/article/details/44783527