41．It is valid to throw (and re-throw) an exception inside a catch(){} clasuse.
42. String Integer Double Date File override the equals() method.
43. The Class class has no constructors.
44. Unicode uses 16-bit to represent a char
UTF uses as many as bits as are needed to represent a char
45. a instanceof b (right)
A instanceof (b) (wrong)
46.double d=-0.5;
Math.ceil(d)=-0.0
Math.floor(d)=-1.0
47. public transient static final int abc=800; (right)
48. String.trim() 是去掉字符串两边的空格
49．Long val=new Long(“11”);
byte bb=val.byteValue();
50. int[] a=new int[]{1,2,3} (right)
51. Java 中&不用于字符串之间的连接
52. interface methods are public, so the method being implemented must be public
53. null object instanceof a class always results in false
54. why define a method native:
1. to get to access hardware that java does not know about
2. to write optimsed code for performance in a language such as C++
55. int[] a=new int[5];
System.out.println(a[5]); runtime error rather than compile error
56．You can obtain a mutually exclusive lock on any object
57．Interface 也是object的子类
58．熟练掌握collection map 部分，包括其中的方法
59．An interface can not be instantiated
60. collection中方法有 isEmpty() toArray() iterator()