第一个程序的错误是i>0，i的取值应该是从0开始的，所以这里应该是i>=0。
test: x=null does not execute the fault.
test: x=[2,3,2];y=2 executes the fault, but does not result in an error state.
test: x=[4,3,1];y=2 results in an error, but not a failure.
第二个程序的错误是for循环语句for (int i = 0; i < x.length; i++)这个语句找的是第一个0，应该是for (int i=x.length-1; i >= 0; i--)这个才是找最后一个0
test:x=null does not execute the fault.
test:x=[0] executes the fault, but does not result in an error state.
test:x=[1,2,0] results in an error, but not a failure.