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