题目：
首先我们需要搞懂fault，error，failure的区别：
百度搜索到的解释：
Software Fault: A static defect in the software;(eg: virus)
Software Failure: External, incorrect behavior with respect to the requirements or other description of the expected behavior;( eg: high body temperature)
Software Error: An incorrect internal state that is the manifestation of some fault;(eg: some symptoms)
我的理解是：
Software Fault: 在编程中出错的那句话，或者是那个错误的方式
Software Failure: 运行结果与预期的不一样就是导致了一个failure
Software Error: 在测试用例运行中，运行了fault的错误方式，就导致了一个error
Answer：
In the first faulty programs:
1、Actual output：-1. Because in the loop i can not get 0, we need to change it.
for(int i=x.length-1;i>=0;i--)
2、 test：x=[] ; y=1
Array x is a null array, throw NullPointerException.
3、 test：x=[0,1,2] ;y=1
Expected=1
Actual = 1
Although it leads to fault, it doesn’t leads to error. Because when i=1, then return i.
4、 test：x=[0,1,2] ;y=3
Expected = -1
Actual = -1
Although it leads to error, the result is right.
In the second faulty programs:
1、Actual output：0 . Because in the first loop x[i]==0,output the i, we need to change it.
for( int i = x.length-1 ; i >= 0 ; i++)
2、test：x=[]
Array x is a null array, throw NullPointerException.
3、 test：x=[0]
Expected=0
Actual = 0
Although it leads to fault ,it doesn’t leads to error. Because x.length=0;
4、 test：x=[1,2,3]
Expected=-1
Actual = -1
Although it leads to error but the result is right