Cov lus qhia rau programming Java daim ntawv thov rau Unix
Yam Zoo Txog Java
Java yog ib qho kev khiav hauj lwm kaw lus nruab nrab rau kev tsim software. Nws yog ib hom lus programming, cov kev pabcuam hluav taws xob thiab ib lub sij hawm khiav mus los. Ib qho Java yuav tsim tau ntawm ib lub computer thiab khiav ntawm lwm lub computer nrog qhov tseeb lub sij hawm ib puag ncig. Feem ntau, cov kev pabcuam Java dhau los muaj peevxwm khiav tau ntawm cov chaw khiav haujlwm tshiab. Java yog nplua nuj txaus tias kev siv cov nyuab heev txawm sau tau ntawv tsis muaj kev khiav hauj lwm ua ke. Qhov no hu ua 100% Java.
Nrog rau kev txhim kho Java Java tau txais hauv cov chaw, vim hais tias thaum koj qhov kev pab cuam rau lub Vev xaib, koj tsis muaj txoj kev paub txog tus txheej txheem twg tus neeg siv yuav nyob rau. Nrog rau lub programming Java, koj tuaj yeem ua kom zoo dua ntawm "sau ib zaug, khiav nyob qhov twg" qhov chaw. Qhov no txhais tau hais tias thaum koj sau koj qhov kev pab cuam Java, koj tsis tsim cov lus qhia rau ib qho kev sib tw. Xwb, koj tsim Java byte code, uas yog, cov lus qhia rau Java Virtual Machine (Java VM). Rau cov neeg siv, nws tsis muaj dab tsi platform lawv siv - Qhov rais, Unix , MacOS, los yog Internet browser-ntev li nws muaj Java VM, nws to taub cov byte codes.
Peb Hom Kev Kawm Ntawm Java
- Ib qho "applet" yog ib qho kev kawm Java uas tsim los nkag rau ntawm nplooj ntawv web page.
- Ib tug "servlet" yog ib qho Java uas tsim los khiav ntawm tus neeg siv khoom.
Hauv no ob qhov kev pabcuam Java tsis tuaj yeem khiav tsis tau cov kev pabcuam los ntawm lub Web browser rau tus kws qhia lossis lub Web server rau ib tus neeg pabcuam.
- Ib "Java daim ntawv thov" yog ib qho kev qhia Java uas tau khiav ntawm nws tus kheej.
Cov lus qhia hauv qab no yog rau koj los ua ib qho Java siv lub tshuab Unix-based.
Daim ntawv txheeb xyuas
Yooj yim yooj yim, koj xav tau tsuas yog ob yam khoom sau ib qho Java program xwb:
(1) Java 2 Platform, Standard Edition (J2SE), yav tas los hu ua Java Development Kit (JDK).
Download tau qhov tseeb version rau Linux. Nco ntsoov tias koj download tau SDK, tsis yog JRE (JRE yog tso rau hauv SDK / J2SE).
(2) Ib phau ntawv nyeem
Yuav luag txhua tus editor koj pom ntawm Unix-based platforms yuav ua (xws li, Vi, Emacs, Pico). Peb yuav siv Pico ua piv txwv.
Kauj Ruam 1. Tsim Java Ntaub Ntawv.
Ib qhov chaw ua ntaub ntawv muaj cov ntawv nyeem hauv Java programming hom lus. Koj tuaj yeem siv cov ntawv nyeem los tsim thiab kho kom raug cov ntaub ntawv.
Koj muaj ob qho kev xaiv:
* Koj tuaj yeem txuag tau daim FatCalories.java (qhov kawg ntawm qhov tsab xov xwm no) mus rau koj lub computer. Txoj kev no yuav txuag tau koj ib co kev ntaus ntawv. Tom qab ntawd, koj tuaj yeem mus ncaj qha mus rau kauj ruam 2.
* Lossis, koj tuaj yeem ua raws li cov lus qhia ntev:
(1) Nqa ib lub plhaub (qee zaum hu ua qhov xaus) qhov rais.
Thaum pib kiag tawm, koj cov npe tam sim no feem ntau yuav yog koj lub tsev directory. Koj tuaj yeem hloov koj cov npe tam sim no rau koj lub tsev directory txhua lub sijhawm los ntawm kev sau cd ntawm qhov sai (feem ntau yog "%") thiab tom qab ntawd nias Rov Qab.
Cov ntaub ntawv Java koj tsim yuav tsum tau khaws cia rau hauv ib qho chaw cais. Koj tuaj yeem tsim ib lub npe los ntawm kev siv cov lus txib mkdir . Piv txwv, kom tsim cov directory java hauv koj lub tsev directory, koj yuav xub hloov koj cov npe tam sim no rau koj cov directory hauv tsev los ntawm qhov kev hais hauv qab no:
% cd
Tom qab ntawd, koj yuav nkag mus rau nram qab no cov lus txib:
% mkdir java
Xav hloov koj cov npe tam sim no rau cov npe tshiab no, koj mam li nkag mus rau: % cd java
Tam sim no koj tuaj yeem pib tsim koj cov ntaub ntawv los.
(2) Pib lub Pico editor los ntawm hom pizza ntawm qhov sai thiab nias xa rov qab. Yog hais tias lub kaw lus teb nrog lus pico: tsis tau hais kom ua , ces Pico feem ntau tsis tuaj yeem. Nrog koj tus neeg ua haujlwm tham txog kev qhia ntxiv, lossis siv lwm tus editor.
Thaum koj pib Pico, nws mam li tso saib tus tshiab, dawb tsis tuaj yeem. Qhov no yog qhov chaw uas koj yuav ntaus koj cov cai.
(3) Ntaus cov code uas teev rau tom kawg ntawm qhov khoom (hauv qab "Qauv Java Program") rau hauv daim ntawv dawb paug. Txhua yam raws nraim li qhia. Java compiler thiab txhais lus yog cov ntaub ntawv-sensitive.
(4) Txuag qhov chaws los ntawm hom Ctrl-O. Thaum koj pom Cov Ntaub Ntawv Lub Npe los sau:, Type FatCalories.java, ua ntej los ntawm cov npe uas koj xav tau cov ntaub ntawv mus. Yog tias koj xav kom FatCalories.java nyob rau hauv cov directory / home / smith / java, ces koj yuav ntaus ntawv
/home/smith/java/FatCalories.java thiab nias rov qab.
Siv Ctrl-X tawm ntawm Pico.
Kauj Ruam 2. Sau cov Ntaub Ntawv Los Siv.
Java compiler, nyeem ntawv, yuav siv koj cov ntaub ntawv ua ntaub ntawv thiab txhais nws cov ntawv nyeem rau hauv cov lus qhia hauv Java Virtual Machine (Java VM) yuav nkag siab. Tus compiler tso cov lus qhia rau hauv ib daim ntawv tso npe ntawm byte.
Tam sim no, coj mus rau lwm lub qhov rais plhaub. Yuav kom muab koj cov ntaub ntawv ua tiav, hloov koj cov npe tam sim no mus rau qhov chaw nyob ntawm koj qhov chaw nyob. Piv txwv, yog tias koj qhov directory directory / tsev / smith / java, koj yuav sau cov lus txib nram qab no ntawm qhov sai thiab nias rov qab:
% cd / home / smith / java
Yog tias koj nkag mus pw rau ntawm qhov tam sim ntawd, koj yuav tsum pom cov npe tam sim no, uas nyob hauv qhov ua piv txwv no tau hloov rau / home / smith / java.
Yog tias koj nkag mus rau ls ntawm qhov sai, koj yuav tsum pom koj cov ntaub ntawv: FatCalories.java.
Tam sim no koj tau compile. Ntawm qhov tam sim no, sau cov lus txib nram qab no thiab nias rov: Javac FatCalories.java
Yog tias koj pom qhov yuam kev no:
javac: hais kom ua tsis pom
ces Unix yuav tsis pom Java compiler, javac.
Ntawm no yog ib txoj kev qhia Unix qhov twg nrhiav javac. Xav tias koj ntsia lub Java 2 Platform (J2SE) hauv /usr/java/jdk1.4. Ntawm qhov kev tshoov siab, ntaus nqe lus nram qab no thiab nias rov qab:
/usr/java/jdk1.4/javac FatCalories.java
Cov compiler tam sim no tau tsim ib cov ntaub ntawv hauv Java byte code: FatCalories.class.
Ntawm lub sijhawm tam sim no, ntaus cov ls los xyuas qhov tseeb ntawm cov ntaub ntawv tshiab.
Kauj Ruam 3. Khiav qhov Program
Java VM yog tsim los ntawm ib tug neeg txhais lus Java hu ua java. Tus neeg txhais lus no yuav siv koj cov ntaub ntawv tso cai thiab siv cov lus qhia los ntawm txhais cov lus qhia hauv koj lub computer kom nkag siab.
Nyob rau tib phau ntawv, sau rau ntawm qhov kev tshau:
java FatCalories
Thaum koj khiav qhov kev zov me nyuam koj yuav tsum nkag mus rau ob tug naj npawb thaum cov kab lus qhia dub tshwm. Qhov kev zov me nyuam yuav tsum tau sau tseg ob tus xov tooj ntxiv rau qhov feem pua ntawm qhov kev zov me nyuam.
Thaum koj tau txais cov lus yuam kev:
Tshaj tawm hauv xov "ntsiab" java.lang.NoClassDefFoundError: FatCalories
Nws txhais tau tias: java tsis pom koj cov ntaub ntawv byte code, FatCalories.class.
Yuav ua li cas: Ib qho ntawm cov chaw java nws nrhiav koj cov ntaub ntawv byte code yog koj cov npe tam sim no. Piv txwv, yog tias koj cov ntaub ntawv byte code nyob hauv / tsev / smith / java, koj yuav tsum hloov koj cov npe tam sim no rau qhov uas sau cov lus hais hauv qab no rau ntawm qhov sai thiab ntaus rov:
cd / tsev / smith / java
Yog tias koj pw pw rau ntawm qhov tam sim no, koj yuav tsum pom / tsev / smith / java. Yog tias koj nkag rau ls ntawm qhov tam sim ntawd, koj yuav tsum pom koj cov ntaub ntawv FatCalories.java thiab FatCalories.class. Tam sim no sau java FatCalories dua.
Yog tias koj tseem muaj teeb meem, tej zaum koj yuav tsum hloov koj tus CLASSPATH kuj sib txawv thiab. Yog xav paub seb qhov no puas tsim nyog, sim "rho tawm" hauv chav kawm nrog cov lus txib nram qab no:
unset CLASSPATH
Tam sim no sau java FatCalories dua. Yog tias qhov kev zov me nyuam ua haujlwm tam sim no, koj yuav tsum hloov koj qhov txawv ntawm CLASSPATH.