Java:thinging in java p158 exercise 1

標籤：

Create a class with a String field that is initialized at the point of definition, and another one that is initialized by the constructor. What is the difference between the two approaches.

 1 class Test{ 2     String s1; 3     String s2="hello world"; 4     String s3; 5     Test(){ 6         s3="hello java"; 7     } 8 } 9 public class ConstructorTest {10 11     public static void main(String[]args){12         13         Test t=new Test();14         System.out.println(t.s1);15         System.out.println(t.s2);16         System.out.println(t.s3);17         18     }19 }

輸出

nullhello worldhello java

 

Java:thinging in java p158 exercise 1