java中字符串初始化的区别

public class JavaTest1 
{ 
   public static void main(String[] args)  
  { 
    String str1 = "java" ; 
    String str2 = new String("java") ; 
    String str3 = "java" ; 
    System.out.println("str1 == str2 ? --- > "+(str1==str2)) ; 
    System.out.println("str1 == str3 ? --- > "+(str1==str3)) ; 
    System.out.println("str3 == str2 ? --- > "+(str3==str2)) ; 
  } 
}