java程序设计基础篇 复习笔记 第四单元

1
think before coding
code incrementally
2
sentinel value
sentinel-controlled loop
3
输入输出重定向 > <
input redirection
output redirection
4
pretest loop
posttest loop
5
从小到大添加浮点数比从大到小精确
6
Integer.toBinaryString(int)
Integer.toHexString(int)
7
PIE =4* (1 - 1 / 3 + 1 / 5 - 1 / 7 ... - 1 / (2 * i - 1) + 1 / (2 * i + 1))

Keyword
break statement
continue statement
do-while loop
for loop
loop control statement
infinite loop
input redirection
iteration
labeled continue statement
loop
loop-condition condition :循环控制条件
loop body
nested body
off-by-one error
output redirection
sentinel value
while loop

4.1
always true
4.2
无限循环
4.3
无限次;9次;9次
11111111111111111
2,4,6,8
3,5,7,9
4.4
循环控制条件和循环体的执行顺序
int sum = 0;
int number = 0;
do{
	sum += number;
	number = input.nextInt();
}while(number != 0)
4.5
相同
4.6
循环初始化,循环控制条件,每次迭代后操作
for(int i = 0;i < 100;i++)System.out.println(i+1);
4.7
max is 5
number is 0
4.8
sum is 14
number is 0
4.9
max is 5
number is 0
4.10
无限循环
4.11
不能
4.12
可以,但是for循环更直接,明晰
4.13
long sum =0;
int i = 0;
while(i <= 1000){
	sum += i++;
}
/*
do{
	sum+=i++;
}while(i<=1000)
*/
4.14
cant because of integer division
4.15
跳出当前循环;跳出当前迭代;能,1;不能
4.16
int sum  = 0;
int i = 1;
for(;sum < 10000;i++)sum += i;
4.17
if(i % 3 == 0){i++;continue;}
4.18
.........
4.19
System.out.println(i);1;
4.20
System.out.println(i);1;
4.21
2 public static void
3:int i 在循环体外声明
5:声明int j 并初始化
7:分号
11:去掉分号
4.22
未初始化;多加了分号;
4.23
0 0 1 0 1 2 3 0 1 2 3 4;
compile Error;
1xxx2xxx4xxx8xxx16xxx
1xxx2xxx4xxx8xxx
1xxx2xxx4xxx
1xxx2xxx
1xxx
;
1G
1G2G
1G2G4G
1G2G4G8G
1G2G4G8G16G
;
4.24
no output result;because the loop never end
4.25
n
n-5
n+1
(n-3)/3

编程题
4.23
//从左向右
double sum = 0;
for(int i =1;i<=50000;i++){
	sum += 1d/i;
}
System.out.println(sum);
//11.397003949278504
//从右向左
double sum = 0;
for(int i = 50000;i >= 1;i--){
	sum += 1d/i;
}
System.out.println(sum);
//11.397003949278519