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1、Java語言程序設(shè)計(jì)Java語言程序設(shè)計(jì)楊巍yangwei@mail.neu.edu.cnJava語言程序設(shè)計(jì)Java編程基礎(chǔ)——語句ControllingExecution楊巍yangwei@mail.neu.edu.cnJava編程基礎(chǔ)Java語句?順序語句:按照從上至下的順序一次執(zhí)行?條件語句:根據(jù)不同條件,執(zhí)行不同的語句?if?if..else..?if..elseif..?if..elseif..elseif…else?switch?循環(huán)語句:重復(fù)執(zhí)行某些動(dòng)作?for?whilie?do…while3Java
2、編程基礎(chǔ)ifStatementsif(Boolean-expression){if(Boolean-expression){statement;statements1;}}elseif(Boolean-expression){statements2;if(Boolean-expression){}elseif(Boolean-expression){statement1;statements3;}else{}else{statement2;statements4;}}4Java編程基礎(chǔ)練習(xí)?判斷一個(gè)數(shù)字是奇數(shù)還是偶數(shù)?
3、如果一個(gè)數(shù)字除以2余數(shù)為0,則肯定是偶數(shù),相反一定是奇數(shù)IfElseDemo.java5Java編程基礎(chǔ)練習(xí)?求出兩個(gè)數(shù)字中的最大值MaxDemo.java6Java編程基礎(chǔ)ifStatements?三目運(yùn)算符Ternaryif-elseoperatorboolean-exp?表達(dá)式1:表達(dá)式2if(Boolean-expression){statement1;}else{statement2;}7Java編程基礎(chǔ)swtichStatements?swtichStatements?多路選擇語句selectionstat
4、ement?用于處理從多個(gè)條件中選擇一個(gè)合適的或是求多個(gè)結(jié)果?Switch語句中選擇值只能是字符或常量?eachcaseendswithabreak?Butthebreakisoptional8Java編程基礎(chǔ)swtichStatementsswtich(integral-selector){SwitchDemo1.javacaseintegral-value1:statements;break;SwitchDemo2.javacaseintegral-value2:statements;break;……caseint
5、egral-valueN:statements;break;default:statements;}9Java編程基礎(chǔ)whileStatements?事先不知道循環(huán)該執(zhí)行多少次?While語句先判斷,后執(zhí)行while(Boolean-expression){statements;increment/decrementcounter;}10while(Boolean-expression){statements;increment/decrementcounter;}循環(huán)條件初值F判斷條件Tstatementorbloc
6、k修改循環(huán)條件Java編程基礎(chǔ)練習(xí)?編寫一個(gè)程序,實(shí)現(xiàn)1~100的累加?通過While語句循環(huán)將100個(gè)數(shù)遍歷一次,再進(jìn)行求和運(yùn)算WhileDemo.java12Java編程基礎(chǔ)do…whileStatements?do…while?Thesoledifferencebetweenwhileanddo-whileisthatthestatementofthedo-whilealwaysexecutesatleastonce,eveniftheexpressionevaluatestofalsethefirsttimed
7、o{statements;increment/decrementcounter;}while(Boolean-expression);13do{statements;increment/decrementcounter;}while(Boolean-expression);循環(huán)條件初值statementorblock修改循環(huán)條件T判斷條件FDoWhileDemo.javaJava編程基礎(chǔ)forStatementsfor(Expression1;Expression2;Expression3){statements;}f
8、or(initialize;Boolean-expression;increment/decrement){statements;}Expression1;while(Expression2){Block;Expression3};15Java編程基礎(chǔ)forStatementsForDemo1.java循環(huán)條件初值ForDemo2