When a relatively large number of operations, pay attention to whether the overflow, especially when integer operations.
Examples 2-29 [a] Frequently Asked Questions
int money = 1000000000; //10亿
int years = 20;
//返回的total是负数，超过了int的范围
int total = money*years;
System.out.println("total="+total);
//返回的total仍然是负数。默认是int，因此结果会转成int值，再转成long。但是已经发生//了数据丢失
long total1 = money*years;
System.out.println("total1="+total1);
//返回的total2正确:先将一个因子变成long，整个表达式发生提升。全部用long来计算。
long total2 = money*((long)years);
System.out.println("total2="+total2);The results shown in Figure 2-8 operation.
FIG Example 2-29 2-8 run renderings
[Example 2-30] Frequently Asked Question two
int l = 2; //分不清是L还是1,
long a = 23451l;//建议使用大写L
System.out.println(l+1);Note:
L and l problem : Do not name a variable named l, l 1 and easily confused. long type uppercase L not small.
