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หลายภาษามีเครื่องมือแบบนี้เช่น python ถึงคิวจาวา  มาใน java 9

REPL สะดวกดีประหยัดเวลาในการจะลองเขียนโค้ดทดสอบสั้นๆ หรือเป็น Console เมื่อต้องการสอนเขียนโปรแกรมก็ได้

pairoch@microbrainLAB:/opt$ jshell -v
| Welcome to JShell -- Version 11.0.9.1
| For an introduction type: /help intro

jshell> int i =0;
i ==> 0
| created variable i : int

jshell> /list

1 : int i =0;

jshell> int b =10;
b ==> 10
| created variable b : int

jshell> /list

1 : int i =0;
2 : int b =10;

jshell> System.out.orintln("Hello");
| Error:
| cannot find symbol
| symbol: method orintln(java.lang.String)
| System.out.orintln("Hello");
| ^----------------^

jshell> System.out.println("Hello");
Hello

jshell> System.out.println("REsult: "+ i+b );
REsult: 010

jshell> System.out.println("REsult: "+ (i+b) );
REsult: 10

jshell> int result = i+b;
result ==> 10
| created variable result : int

jshell> System.out.println("REsult: "+ result );
REsult: 10

jshell> /list

1 : int i =0;
2 : int b =10;
3 : System.out.println("Hello");
4 : System.out.println("REsult: "+ i+b );
5 : System.out.println("REsult: "+ (i+b) );
6 : int result = i+b;
7 : System.out.println("REsult: "+ result );

jshell> void helloJShell(int i){
...> for (int x =0; x<i; x++) System.out.println("HEllo "+x);
...> }
| created method helloJShell(int)

jshell> /list

1 : int i =0;
2 : int b =10;
3 : System.out.println("Hello");
4 : System.out.println("REsult: "+ i+b );
5 : System.out.println("REsult: "+ (i+b) );
6 : int result = i+b;
7 : System.out.println("REsult: "+ result );
8 : void helloJShell(int i){
for (int x =0; x<i; x++) System.out.println("HEllo "+x);
}

jshell> helloJShell(3)
HEllo 0
HEllo 1
HEllo 2

jshell> helloJShell(4);
HEllo 0
HEllo 1
HEllo 2
HEllo 3

jshell> /list

1 : int i =0;
2 : int b =10;
3 : System.out.println("Hello");
4 : System.out.println("REsult: "+ i+b );
5 : System.out.println("REsult: "+ (i+b) );
6 : int result = i+b;
7 : System.out.println("REsult: "+ result );
8 : void helloJShell(int i){
for (int x =0; x<i; x++) System.out.println("HEllo "+x);
}
9 : helloJShell(3)
10 : helloJShell(4);

jshell> helloJShell(result)
HEllo 0
HEllo 1
HEllo 2
HEllo 3
HEllo 4
HEllo 5
HEllo 6
HEllo 7
HEllo 8
HEllo 9

jshell> helloJShell(12)
HEllo 0
HEllo 1
HEllo 2
HEllo 3
HEllo 4
HEllo 5
HEllo 6
HEllo 7
HEllo 8
HEllo 9
HEllo 10
HEllo 11

jshell> if (result < 10)System.out.println("result less than 10");

jshell> /list

1 : int i =0;
2 : int b =10;
3 : System.out.println("Hello");
4 : System.out.println("REsult: "+ i+b );
5 : System.out.println("REsult: "+ (i+b) );
6 : int result = i+b;
7 : System.out.println("REsult: "+ result );
8 : void helloJShell(int i){
for (int x =0; x<i; x++) System.out.println("HEllo "+x);
}
9 : helloJShell(3)
10 : helloJShell(4);
11 : helloJShell(result)
12 : helloJShell(43)
13 : if (result < 10)System.out.println("result less than 10");

jshell> if (result == 10)System.out.println("ryes");
ryes

jshell> helloJShell(5)
HEllo 0
HEllo 1
HEllo 2
HEllo 3
HEllo 4

jshell> /import
| import java.io.*
| import java.math.*
| import java.net.*
| import java.nio.file.*
| import java.util.*
| import java.util.concurrent.*
| import java.util.function.*
| import java.util.prefs.*
| import java.util.regex.*
| import java.util.stream.*

jshell> /exit
| Goodbye
pairoch@microbrainLAB:/opt$