Chapter 5: Loop
One.while loop
1. Flow chart
2. Attention
Only when the loop contains only one statement or no statement, you can omit the curly braces.
In loop control, do not use floating-point values to compare for equality, because floating-point values are approximate values.
3. Classic case
int i=1;
while(i<10)
if((i++)%2==0)
System.out.print(i+" ");//3 5 7 9
Two. do-while loop
1. Flow chart The
other two are pre-test loops, and do-while is post-test loop
Three. for loop
1. Flow chart
2. Grammar
for (initial operation; loop continuation condition; operation after each iteration) ( loop body; statement group; } break: jump out of the current loop continue: jump out of the current iteration return: jump out of the current method
3. Attention
It is a good habit to declare variables in the initial operation of the for loop
The initial actions can be separated by commas
for(int i=0,j=0;i+j<10;i++,j++){
}
Operations after each iteration can be separated by commas
for（int i=0;i<10;System.out.println(i),i++)
In infinite loop
for(;true;){
}
while(true){
}//建议用这种
Four. Input and output redirection
1. When the amount of data is large, you can use input and output redirection
java 类名 < input.txt//向input.txt中读文件
java 类名 > output.txt//向output.txt中写文件
java 类名 < input.txt > output.txt//从input.txt中读，再写入output.txt文件中
2. Specific cases
Use input redirection
Integers are separated by spaces in the txt text
Use output redirection
Five. Bit operator
| Operator | description |
|---|---|
| & | Bit and |
| | | Bit or |
| ^ | Bit and or |
| ~ | Negate |
| << | Shift left |
| >> | Right shift |
| >>> | Unsigned right shift |
1. Left shift
int y=10<<2;//00001010->00101000 结果为40
Binary moves two bits to the left and adds two zeros
2. Right shift
int y=10>>2;//00001010 -> 00000010 结果为2
int y=-10>>2;//结果为-3
Shift positive numbers to the right to complement 0,
negative numbers Shift to the right to complement 1
3. Shift right unsigned bit
int y=10>>>2;//结果为2
No matter positive or negative, add 0
V. Summary
Through the study of Chapter 5, I have learned three kinds of loops, while loop, do-while loop and for loop. They are used in different scenarios and can be transformed into each other most of the time. Use continue and break as little as possible to improve the code. readability. Input and output redirection solves the problem of large data volume very well, and the shift operation is very efficient when performing binary calculations.
Come on! Chapter 6 To Be More...