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7. Scala process control
2022-07-05 00:33:00 【liangzai2048】
List of articles
Process control
Branch control if-else
Let the program execute selectively , There are three branches ： Single branch 、 Double branch 、 Multiple branches
Single branch
- Basic grammar
if ( Conditional expression ) {
Execute code block
}
explain ： When the conditional expression is true when , Will execute () Code for .
- Case study
demand ： Enter the age of the person , If the comrade is younger than 18 year , The output “ A minor ”
Double branch
- Basic grammar
if ( Conditional expression ) {
Execute code block 1
} else {
Execute code block 2
}
explain ： When the conditional expression is true when , Will execute () Code for
When the conditional expression is false when , Will execute else Code for
- Case study
demand ： Enter the age of the person , If the comrade is younger than 18 year , The output “ A minor ”, Otherwise output “ adult ”
Multiple branches
- Basic grammar
if ( Conditional expression 1) {
Execute code block
} else if ( Conditional expression 2) {
Execute code block
}else if ( Conditional expression 3) {
Execute code block
}
...
else if ( Conditional expression n) {
Execute code block
} else {
Execute code block
}
explain ： When the conditional expression is true when , Will execute () Code for
When the conditional expression is false when , Will execute else Code for
- Case study
demand ：
When the age is less than or equal to 6 Time output “ childhood ”
When the age is less than 18 Time output “ A minor ”
When the age is less than 35 Time output “ adult ”
When the age is less than 60 Time output “ middle-aged ”
Otherwise output “ The elderly ”
package day04
import scala.io.StdIn
object Test01_IfElse {
def main(args: Array[String]): Unit = {
println(" Please enter your age :")
val age: Int = StdIn.readInt()
// 1、 Single branch
if (age >= 18) {
println(" adult ")
}
println("===============")
// 2、 Double branch
if (age >= 18) {
println(" adult ")
} else {
println(" A minor ")
}
println("=============")
// 3、 Multiple branches
if (age <= 6) {
println(" childhood ")
} else if (age < 18) {
println(" A minor ")
} else if (age < 35) {
println(" adult ")
} else if (age < 60) {
println(" middle-aged ")
} else {
println(" The elderly ")
}
}
}
Output results ：
Please enter your age :
24
adult
===============
adult
=============
adult
The return value of the branch statement
package day04
import scala.io.StdIn
object Test01_IfElse {
def main(args: Array[String]): Unit = {
println(" Please enter your age ")
val age: Int = StdIn.readInt()
// The return value of the branch statement
val result: String = if (age <= 6) {
println(" childhood ")
" childhood "
} else if (age < 18) {
println(" A minor ")
" A minor "
} else if (age < 35) {
println(" adult ")
" adult "
} else if (age < 60) {
println(" middle-aged ")
" middle-aged "
} else {
println(" The elderly ")
" The elderly "
}
println("result:" + result)
}
}
Output results ：
Please enter your age
24
adult
result: adult
package day04
import scala.io.StdIn
object Test01_IfElse {
def main(args: Array[String]): Unit = {
println(" Please enter your age ")
val age: Int = StdIn.readInt()
// The return value of the branch statement
val result1: String = if (age <= 6) {
println(" childhood ")
" childhood "
} else if (age < 18) {
println(" A minor ")
" A minor "
} else if (age < 35) {
println(" adult ")
" adult "
} else if (age < 60) {
println(" middle-aged ")
" middle-aged "
} else {
println(" The elderly ")
" The elderly "
}
println("result1:" + result1)
}
}
Output results ：
Please enter your age
24
adult
result:()
package day04
import scala.io.StdIn
object Test01_IfElse {
def main(args: Array[String]): Unit = {
println(" Please enter your age ")
val age: Int = StdIn.readInt()
// The return value of the branch statement
val result2: Any = if (age <= 6) {
println(" childhood ")
" childhood "
} else if (age < 18) {
println(" A minor ")
age
} else if (age < 35) {
println(" adult ")
age
} else if (age < 60) {
println(" middle-aged ")
age
} else {
println(" The elderly ")
age
}
println("result2:" + result2)
}
}
Output results ：
Please enter your age
25
adult
result2:25
Any You can return any type of return value
Scala There is no ternary operator
package day04
import scala.io.StdIn
object Test01_IfElse {
def main(args: Array[String]): Unit = {
println(" Please enter your age ")
val age: Int = StdIn.readInt()
// Scala There is no ternary operator String res2 = (age >=18)? " adult " : " A minor "
val res: String = if (age >= 18) {
" adult "
} else {
" A minor "
}
println("res" + res)
println("============")
val res2 = if (age >= 18) " adult " else " A minor "
println("res2" + res2)
// String res3 = (age >=18)? " adult " : " A minor "
}
}
Output results ：
Please enter your age
25
res adult
============
res2 adult
Nested statement
package day04
import scala.io.StdIn
object Test01_IfElse {
def main(args: Array[String]): Unit = {
println(" Please enter your age :")
val age: Int = StdIn.readInt()
// 5、 Nesting branches
if (age >= 18) {
println(" adult ")
if (age >= 35) {
if (age >= 60) {
println(" The elderly ")
} else {
println(" middle-aged ")
}
}
} else {
println(" A minor ")
if (age <= 6) {
println(" childhood ")
}
}
}
}
Output results ：
Please enter your age :
23
adult
For Cycle control
Scala Also for the for Loop, a common control structure, provides many features , these for The nature of the cycle is called for Derivation or for expression .
Range data cycle (To)
- Basic grammar
for (i < -1 to 3) {
print(i + " ")
}
println()
i The variable representing the loop ,<- Regulations to
i Will be from 1-3 loop , Close back and forth
Case study
demand ： Output 5 sentence " handsome young man , You are handsome ！"
package day04
object Test02_ForLoop {
def main(args: Array[String]): Unit = {
// java for grammar ：for(int i = 0;i < 5;i++){System.out.println(i + ".hello world");}
// Range traversal
for (i <- 1 to 5) {
println(i + ". handsome young man , You are handsome ！")
}
println("===============")
for (i <- 6.to(10)) {
println(i + ". handsome young man , You are handsome ！")
}
println("===============")
for (i <- Range(1, 10)) {
println(i + ". handsome young man , You are handsome ！")
}
println("===============")
for (i <- 1 until (10)) {
println(i + ". handsome young man , You are handsome ！")
}
}
}
Output results ：
G:\Java\jdk\bin\java.exe "-javaagent:F:\IDEA2021.3.1qiye\IntelliJ IDEA 2021.3.1\lib\idea_rt.jar=54760:F:\IDEA2021.3.1qiye\IntelliJ IDEA 2021.3.1\bin" -Dfile.encoding=UTF-8 -classpath G:\java\jdk\jre\lib\charsets.jar;G:\java\jdk\jre\lib\deploy.jar;G:\java\jdk\jre\lib\ext\access-bridge-64.jar;G:\java\jdk\jre\lib\ext\cldrdata.jar;G:\java\jdk\jre\lib\ext\dnsns.jar;G:\java\jdk\jre\lib\ext\jaccess.jar;G:\java\jdk\jre\lib\ext\jfxrt.jar;G:\java\jdk\jre\lib\ext\localedata.jar;G:\java\jdk\jre\lib\ext\nashorn.jar;G:\java\jdk\jre\lib\ext\sunec.jar;G:\java\jdk\jre\lib\ext\sunjce_provider.jar;G:\java\jdk\jre\lib\ext\sunmscapi.jar;G:\java\jdk\jre\lib\ext\sunpkcs11.jar;G:\java\jdk\jre\lib\ext\zipfs.jar;G:\java\jdk\jre\lib\javaws.jar;G:\java\jdk\jre\lib\jce.jar;G:\java\jdk\jre\lib\jfr.jar;G:\java\jdk\jre\lib\jfxswt.jar;G:\java\jdk\jre\lib\jsse.jar;G:\java\jdk\jre\lib\management-agent.jar;G:\java\jdk\jre\lib\plugin.jar;G:\java\jdk\jre\lib\resources.jar;G:\java\jdk\jre\lib\rt.jar;F:\IDEADEMO\ScalaLearnDemo\target\classes;G:\java\scala\scala-2.12.11\lib\scala-library.jar;G:\java\scala\scala-2.12.11\lib\scala-parser-combinators_2.12-1.0.7.jar;G:\java\scala\scala-2.12.11\lib\scala-reflect.jar;G:\java\scala\scala-2.12.11\lib\scala-swing_2.12-2.0.3.jar;G:\java\scala\scala-2.12.11\lib\scala-xml_2.12-1.0.6.jar day04.Test02_ForLoop
1. handsome young man , You are handsome ！
2. handsome young man , You are handsome ！
3. handsome young man , You are handsome ！
4. handsome young man , You are handsome ！
5. handsome young man , You are handsome ！
===============
6. handsome young man , You are handsome ！
7. handsome young man , You are handsome ！
8. handsome young man , You are handsome ！
9. handsome young man , You are handsome ！
10. handsome young man , You are handsome ！
===============
1. handsome young man , You are handsome ！
2. handsome young man , You are handsome ！
3. handsome young man , You are handsome ！
4. handsome young man , You are handsome ！
5. handsome young man , You are handsome ！
6. handsome young man , You are handsome ！
7. handsome young man , You are handsome ！
8. handsome young man , You are handsome ！
9. handsome young man , You are handsome ！
===============
1. handsome young man , You are handsome ！
2. handsome young man , You are handsome ！
3. handsome young man , You are handsome ！
4. handsome young man , You are handsome ！
5. handsome young man , You are handsome ！
6. handsome young man , You are handsome ！
7. handsome young man , You are handsome ！
8. handsome young man , You are handsome ！
9. handsome young man , You are handsome ！
A collection of traverse
package day04
object Test02_ForLoop {
def main(args: Array[String]): Unit = {
// 2、 A collection of traverse
for (i <- Array(12, 34, 56, 23)) {
println(i)
}
for (i <- List(12, 34, 56, 23)) {
println(i)
}
for (i <- Set(12, 34, 56, 23)) {
println(i)
}
}
}
Running results ：
12
34
56
23
12
34
56
23
12
34
56
23
Cycle guard
- Basic grammar
for (i <- 1 to 3 if i != 2) {
println(i + " ")
}
Cycle guard , Cycle protection mode （ Also known as conditional judgment , The guards ）. The protection type is true Then go inside the circulatory body , by false Then skip , Be similar to continue（Scala There is no ）
The above code is equivalent to
for (i <- 1 to 3) {
if (1 != 2) {
println(i + " ")
}
}
- Case study
package day04
object Test02_ForLoop {
def main(args: Array[String]): Unit = {
// 3、 Cycle guard
for (i <- 1 to 10) {
if (i != 5) {
println(i)
}
}
println("===============")
for (i <- 1 to 10 if i != 5) {
println(i)
}
}
}
Output results ：
1
2
3
4
6
7
8
9
10
===============
1
2
3
4
6
7
8
9
10
Cycle step
Step cannot be 0
package day04
object Test02_ForLoop {
def main(args: Array[String]): Unit = {
// 4、 Cycle step
for (i <- 1 to 10 by 2) {
println(i)
}
println("===============")
for (i <- 13 to 30 by 3) {
println(i)
}
println("===============")
for (i <- 30 to 13 by -2) {
println(i)
}
println("===============")
for (i <- 10 to 1 by -1) {
println(i)
}
println("===============")
for (i <- 1 to 10 reverse) {
println(i)
}
println("===============")
for (data <- 1.0 to 10.0 by 0.5) {
println(data)
}
}
}
Output results ：
1
3
5
7
9
===============
13
16
19
22
25
28
===============
30
28
26
24
22
20
18
16
14
===============
10
9
8
7
6
5
4
3
2
1
===============
10
9
8
7
6
5
4
3
2
1
===============
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
Nested loop
- Basic grammar
for (i <-1 to 3; j <- 1 to 3) {
println("i = " + i + "j =" + j)
}
No keywords , So we must add ; To cut off logic
- The above code is equivalent to
for (i <- 1 to 3) {
for (j <-1 to 3) {
println("i = " + i + "j =" + j)
}
}
- Case study
package day04
object Test02_ForLoop {
def main(args: Array[String]): Unit = {
// 5、 A nested loop
for (i <- 1 to 3) {
for (j <- 1 to 3) {
println("i = " + i + " j =" + j)
}
}
println("===============")
for (i <- 1 to 3; j <- 1 to 3) {
println("i = " + i + " j =" + j)
}
}
}
Output results ：
i = 1 j =1
i = 1 j =2
i = 1 j =3
i = 2 j =1
i = 2 j =2
i = 2 j =3
i = 3 j =1
i = 3 j =2
i = 3 j =3
===============
i = 1 j =1
i = 1 j =2
i = 1 j =3
i = 2 j =1
i = 2 j =2
i = 2 j =3
i = 3 j =1
i = 3 j =2
i = 3 j =3
multiplication table
package day04
// Output the multiplication table
object Test03_Practice_MulTable {
def main(args: Array[String]): Unit = {
for (i <- 1 to 9) {
for (j <- 1 to i) {
print(s"$j * $i = ${i * j}\t")
}
println()
}
println("=========================")
// Abbreviation
for (i <- 1 to 9; j <- 1 to i) {
print(s"$j * $i = ${i * j}\t")
if (j == i) println()
}
}
}
Output results ：
G:\Java\jdk\bin\java.exe "-javaagent:F:\IDEA2021.3.1qiye\IntelliJ IDEA 2021.3.1\lib\idea_rt.jar=55763:F:\IDEA2021.3.1qiye\IntelliJ IDEA 2021.3.1\bin" -Dfile.encoding=UTF-8 -classpath G:\java\jdk\jre\lib\charsets.jar;G:\java\jdk\jre\lib\deploy.jar;G:\java\jdk\jre\lib\ext\access-bridge-64.jar;G:\java\jdk\jre\lib\ext\cldrdata.jar;G:\java\jdk\jre\lib\ext\dnsns.jar;G:\java\jdk\jre\lib\ext\jaccess.jar;G:\java\jdk\jre\lib\ext\jfxrt.jar;G:\java\jdk\jre\lib\ext\localedata.jar;G:\java\jdk\jre\lib\ext\nashorn.jar;G:\java\jdk\jre\lib\ext\sunec.jar;G:\java\jdk\jre\lib\ext\sunjce_provider.jar;G:\java\jdk\jre\lib\ext\sunmscapi.jar;G:\java\jdk\jre\lib\ext\sunpkcs11.jar;G:\java\jdk\jre\lib\ext\zipfs.jar;G:\java\jdk\jre\lib\javaws.jar;G:\java\jdk\jre\lib\jce.jar;G:\java\jdk\jre\lib\jfr.jar;G:\java\jdk\jre\lib\jfxswt.jar;G:\java\jdk\jre\lib\jsse.jar;G:\java\jdk\jre\lib\management-agent.jar;G:\java\jdk\jre\lib\plugin.jar;G:\java\jdk\jre\lib\resources.jar;G:\java\jdk\jre\lib\rt.jar;F:\IDEADEMO\ScalaLearnDemo\target\classes;G:\java\scala\scala-2.12.11\lib\scala-library.jar;G:\java\scala\scala-2.12.11\lib\scala-parser-combinators_2.12-1.0.7.jar;G:\java\scala\scala-2.12.11\lib\scala-reflect.jar;G:\java\scala\scala-2.12.11\lib\scala-swing_2.12-2.0.3.jar;G:\java\scala\scala-2.12.11\lib\scala-xml_2.12-1.0.6.jar day04.Test03_Practice_MulTable
1 * 1 = 1
1 * 2 = 2 2 * 2 = 4
1 * 3 = 3 2 * 3 = 6 3 * 3 = 9
1 * 4 = 4 2 * 4 = 8 3 * 4 = 12 4 * 4 = 16
1 * 5 = 5 2 * 5 = 10 3 * 5 = 15 4 * 5 = 20 5 * 5 = 25
1 * 6 = 6 2 * 6 = 12 3 * 6 = 18 4 * 6 = 24 5 * 6 = 30 6 * 6 = 36
1 * 7 = 7 2 * 7 = 14 3 * 7 = 21 4 * 7 = 28 5 * 7 = 35 6 * 7 = 42 7 * 7 = 49
1 * 8 = 8 2 * 8 = 16 3 * 8 = 24 4 * 8 = 32 5 * 8 = 40 6 * 8 = 48 7 * 8 = 56 8 * 8 = 64
1 * 9 = 9 2 * 9 = 18 3 * 9 = 27 4 * 9 = 36 5 * 9 = 45 6 * 9 = 54 7 * 9 = 63 8 * 9 = 72 9 * 9 = 81
1 * 1 = 1
1 * 2 = 2 2 * 2 = 4
1 * 3 = 3 2 * 3 = 6 3 * 3 = 9
1 * 4 = 4 2 * 4 = 8 3 * 4 = 12 4 * 4 = 16
1 * 5 = 5 2 * 5 = 10 3 * 5 = 15 4 * 5 = 20 5 * 5 = 25
1 * 6 = 6 2 * 6 = 12 3 * 6 = 18 4 * 6 = 24 5 * 6 = 30 6 * 6 = 36
1 * 7 = 7 2 * 7 = 14 3 * 7 = 21 4 * 7 = 28 5 * 7 = 35 6 * 7 = 42 7 * 7 = 49
1 * 8 = 8 2 * 8 = 16 3 * 8 = 24 4 * 8 = 32 5 * 8 = 40 6 * 8 = 48 7 * 8 = 56 8 * 8 = 64
1 * 9 = 9 2 * 9 = 18 3 * 9 = 27 4 * 9 = 36 5 * 9 = 45 6 * 9 = 54 7 * 9 = 63 8 * 9 = 72 9 * 9 = 81
Introduce variables
- Basic grammar
for (i <- 1 to 3;j = 4 - i) {
println("i =" + i + " j =" + j)
}
- for When there are more than one expression in a row of the derivation , So add ; To cut off logic
- for The derivation has an unwritten Convention : When for Use parentheses when the derivation contains only a single expression , When multiple expressions are included , Usually one expression per line , And use curly braces instead of parentheses , as follows
for {
i <- 1 to 3
j = 4 - i
} {
println("i =" + i + " j =" + j)
}
- Case study
package day04
object Test02_ForLoop {
def main(args: Array[String]): Unit = {
// 5、 A nested loop
for (i <- 1 to 3) {
for (j <- 1 to 3) {
println("i = " + i + " j =" + j)
}
}
println("===============")
for (i <- 1 to 3; j <- 1 to 3) {
println("i = " + i + " j =" + j)
}
println("===============")
// 6、 Loop introduces variables
for (i <- 1 to 10) {
val j = 10 - i
println("i =" + i + " j =" + j)
}
println("===============")
for (i <- 1 to 10; j = 10 - i) {
println("i =" + i + " j =" + j)
}
}
}
Output results ：
i =1 j =9
i =2 j =8
i =3 j =7
i =4 j =6
i =5 j =5
i =6 j =4
i =7 j =3
i =8 j =2
i =9 j =1
i =10 j =0
===============
i =1 j =9
i =2 j =8
i =3 j =7
i =4 j =6
i =5 j =5
i =6 j =4
i =7 j =3
i =8 j =2
i =9 j =1
i =10 j =0
Nine story demon tower
package day04
object Test_04Practice_Pyramid {
def main(args: Array[String]): Unit = {
for (i <- 1 to 9) {
val stars = 2 * i -1
val spaces = 9 - i
println(" " * spaces + "*" * stars)
}
println("==========")
for (i <- 1 to 9;stars = 2 * i;spaces = 9 -i) {
println(" " * spaces + "*" * stars)
}
println("==========")
for (stars <- 1 to 17 by 2;spaces = (17 - stars) / 2) {
println(" " * spaces + "*" * stars)
}
}
}
Output results ：
G:\Java\jdk\bin\java.exe "-javaagent:F:\IDEA2021.3.1qiye\IntelliJ IDEA 2021.3.1\lib\idea_rt.jar=56097:F:\IDEA2021.3.1qiye\IntelliJ IDEA 2021.3.1\bin" -Dfile.encoding=UTF-8 -classpath G:\java\jdk\jre\lib\charsets.jar;G:\java\jdk\jre\lib\deploy.jar;G:\java\jdk\jre\lib\ext\access-bridge-64.jar;G:\java\jdk\jre\lib\ext\cldrdata.jar;G:\java\jdk\jre\lib\ext\dnsns.jar;G:\java\jdk\jre\lib\ext\jaccess.jar;G:\java\jdk\jre\lib\ext\jfxrt.jar;G:\java\jdk\jre\lib\ext\localedata.jar;G:\java\jdk\jre\lib\ext\nashorn.jar;G:\java\jdk\jre\lib\ext\sunec.jar;G:\java\jdk\jre\lib\ext\sunjce_provider.jar;G:\java\jdk\jre\lib\ext\sunmscapi.jar;G:\java\jdk\jre\lib\ext\sunpkcs11.jar;G:\java\jdk\jre\lib\ext\zipfs.jar;G:\java\jdk\jre\lib\javaws.jar;G:\java\jdk\jre\lib\jce.jar;G:\java\jdk\jre\lib\jfr.jar;G:\java\jdk\jre\lib\jfxswt.jar;G:\java\jdk\jre\lib\jsse.jar;G:\java\jdk\jre\lib\management-agent.jar;G:\java\jdk\jre\lib\plugin.jar;G:\java\jdk\jre\lib\resources.jar;G:\java\jdk\jre\lib\rt.jar;F:\IDEADEMO\ScalaLearnDemo\target\classes;G:\java\scala\scala-2.12.11\lib\scala-library.jar;G:\java\scala\scala-2.12.11\lib\scala-parser-combinators_2.12-1.0.7.jar;G:\java\scala\scala-2.12.11\lib\scala-reflect.jar;G:\java\scala\scala-2.12.11\lib\scala-swing_2.12-2.0.3.jar;G:\java\scala\scala-2.12.11\lib\scala-xml_2.12-1.0.6.jar day04.Test_04Practice_Pyramid
*
***
*****
*******
*********
***********
*************
***************
*****************
==========
**
****
******
********
**********
************
**************
****************
******************
==========
*
***
*****
*******
*********
***********
*************
***************
*****************
Loop return value
- Basic grammar
val res = for (i <- 1 to 10) yield i
println(res)
explain ： Return the results processed during traversal to a new Vector Collection , Use yield keyword .
Be careful ： Rarely used in development
- Case study
demand ： Multiply all values in the original data by 2, And return the data to a new set .
package day04
object Test02_ForLoop {
def main(args: Array[String]): Unit = {
// 6、 Loop return value
val a: Unit = for (i <- 1 to 10) {
i
}
println("a =" + a)
println("===============")
val b = for (i <- 1 to 10) {
i
}
println("b =" + b)
println("===============")
val c = for (i <- 1 to 10) yield i
println("c =" + c)
println("===============")
val ints = for (i <- 1 to 10) yield i
val d = ints
println("d =" + d)
println("===============")
val e: IndexedSeq[Int] = for (i <- 1 to 10) yield i
println("e =" + e)
}
}
Output results ：
a =()
===============
b =()
===============
c =Vector(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
===============
d =Vector(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
===============
e =Vector(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
While and do…While Cycle control
While and do…While The use of and Java The usage is the same in language .
While Cycle control
- Basic grammar
Loop variable initialization
while( The loop condition ) {
The loop body ( sentence )
Loop variable iteration
}
explain ：
1、 A loop condition is an expression that returns a Boolean value
2、while A loop is to judge before executing a statement
3、 And for The statements are different ,while Statement has no return value , The whole while The result of the statement is Unit type ()
4、 because while There is no return value , So when you want to use this statement to calculate the return result , It's inevitable to use variables , Variables need to be declared in while The outside of the cycle , So it's equivalent to the inside of the loop having an impact on the outside variables , So... Is not recommended , It's recommended for loop .
Case study
package day04
object Test05_WhileLoop {
def main(args: Array[String]): Unit = {
// while
var a: Int = 10
while (a >= 1) {
println(" This is a while loop : " + a)
a -= 1
}
var b: Int = 0
do {
println(" This is a do-while loop : " + b)
b -= 1
} while (b > 0)
}
}
Output results ：
This is a while loop : 10
This is a while loop : 9
This is a while loop : 8
This is a while loop : 7
This is a while loop : 6
This is a while loop : 5
This is a while loop : 4
This is a while loop : 3
This is a while loop : 2
This is a while loop : 1
This is a do-while loop : 0
Cycle break
- Basic explanation
Scala The built-in control structure specifically removes break and continue, In order to better adapt to functional programming , It is recommended to use the functional style to solve break and continue The function of , Not a keyword .Scala Use in breakable Control structure to achieve break and continue function .
- Case study
demand ：
1、 Throw an exception , Exit loop
2、 Use Scala Medium Breaks Class break Method , Throw and catch exceptions
package day04
import scala.util.control.Breaks
object Test06_Break {
def main(args: Array[String]): Unit = {
// 1、 Throw an exception , Exit loop
try {
for (i <- 0 until 5) {
if (i == 3)
throw new RuntimeException
println(i)
}
} catch {
case e: Exception => // Don't do anything? , Just exit the loop
}
println("=================")
// 2、 Use Scala Medium Breaks Class break Method , Throw and catch exceptions
Breaks.breakable(
for (i <- 0 until 5) {
if (i == 3)
Breaks.break()
println(i)
}
)
println(" This is the code outside the loop ")
}
}
Running results ：
0
1
2
=================
0
1
2
This is the code outside the loop
breakable Original code
def breakable(op: => Unit) {
try {
op
} catch {
case ex: BreakControl =>
if (ex ne breakException) throw ex
}
}
Optimize
Guide pack
import scala.util.control.Breaks._
package day04
import scala.util.control.Breaks
import scala.util.control.Breaks._
object Test06_Break {
def main(args: Array[String]): Unit = {
// 2、 Use Scala Medium Breaks Class break Method , Throw and catch exceptions
breakable(
for (i <- 0 until 5) {
if (i == 3)
break()
println(i)
}
)
println(" This is the code outside the loop ")
}
}
Running results ：
0
1
2
This is the code outside the loop
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