ljy练习题.docx
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ljy练习题.docx
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ljy练习题
1
对象,
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有,不可以
有_键值对映关系,值value,键值key
2.
1.for(inti=0;i System.out.println(list.get(i)); 2.程序运行结果: Hello World Learn Java 3.Hello Learn 4.C 51)publicvoidwork(){ System.out.println(getName()+"work");} @Override publicbooleanequals(Objectobj){ Workeruser=(Worker)obj; Workeruser1=newWorker(); user1=(Worker)obj; if(obj! =null){ returnthis.name.equals(user1.name)&&this.age==(user1.getAge()); } returntrue;} @Override publicinthashCode(){ intresult=0; if(name! =null){result=name.hashCode();} returnresult+age; //TODOAuto-generatedmethodstub }} packageuser; importjava.util.ArrayList; importjava.util.HashSet; importjava.util.Iterator; importjava.util.List; publicclassdad{ publicstaticvoidmain(Stringargs[]){ Workeru=newWorker(); u.setAge(18); u.setName("zhang3"); u.setSalary(3000); Workeru2=newWorker(); u2.setAge(25); u2.setName("li4"); u2.setSalary(3500); Workert2=newWorker(); t2.setAge(22); t2.setName("wang5"); t2.setSalary(3200);/* */*1)创建一个List,在List *中增加三个工人,基本信息如下: 姓名年龄 *工资Salaryzhang3183000li4 *253500wang5223200 */ intty=0; intty1=0; Listlist=newArrayList(); list.add(u); list.add(u2); list.add(t2); for(inti=0;i System.out.print(list.get(i)); } System.out.println("==================="); for(inti2=0;i2 Stringsa=list.get(i2).toString(); if(sa.equals(u2.toString())){ System.out.println(i2); ty=i2; } } Workert3=newWorker(); t3.setAge(24); t3.setName("zhao6"); t3.setSalary(3200); Workeruu=newWorker(); list.add(ty,t3);//在li4之前插入一个工人,信息为: 姓名: zhao6,年龄: 24,工资3300 System.out.println("==================="); for(inti=0;i System.out.println(list.get(i));//利用for循环遍历,打印List中所有工人的信息 } list.remove(t2);//删除wang5的信息 System.out.println("==================="); for(inti=0;i System.out.println(list.get(i));//利用for循环遍历,打印List中所有工人的信息 } System.out.println("==================="); for(inti2=0;i2 Stringsa=list.get(i2).toString(); if(sa.equals(u2.toString())){ System.out.println(i2); u2.work(); } if(sa.equals(u.toString())){ System.out.println(i2); u.work(); } if(sa.equals(t2.toString())){ System.out.println(i2); t2.work(); } if(sa.equals(t3.toString())){ System.out.println(i2); t3.work(); } } Workert4=newWorker(); t4.setAge(24); t4.setName("zhao6"); t4.setSalary(3200); HashSets=newHashSet(); s.add(t4); s.add(t3); s.add(t2); System.out.println("==================="); Iteratorit=s.iterator(); //判断当前的迭代器是否还存在元素, while(it.hasNext()){ //打印元素 System.out.println(it.next()); } System.out.println("==================="); 6C 7importjava.util.*; classWorker{ Stringname; intage; doublesalary; publicWorker(){} publicWorker(Stringname,intage,doublesalary){ this.name=name; this.age=age; this.salary=salary; } PublicinthashCode(){ returnname.hashCode()+age+(int)salary; } publicbooleanequals(Workerw){ w=(Worker)obj; if(w.name==name&&w.salary==salary&&w.age==age){ returntrue; }elsereturnfalse; } } publicclassTestWorker{ publicstaticvoidmain(Stringargs[]){ Setset=newHashSet(); set.add(newWorker(“tom”,18,2000)); set.add(newWorker(“tom”,18,2000)); set.add(0,newWorker(“jerry”,18,2000));//不正确hashset的add方法木有在第几位添加制定数据的方法,故删除”0,” System.out.println(set.size()); } } 8. intresult=0; if(name! =null){result=name.hashCode();} returnresult+age; 将hashcode方法改写为以上即可. 9publicintcompareTo(Objecto){ Workeruser=(Worker)o; intres=user.age 1: (user.age==this.age? 0: -1); if(res==0){ inta=(int)this.salary; intb=(int)user.salary; if(a>b){ return1; }elseif(a==b){ { intrdd=pareTo(user.name);//为什么更换变量之后会改变自然排列顺序,先初始变量,再后来变量 returnrdd; } }else{ return-1; } } returnres; } 10.1替换原映射,2新建映射,3只能移除key值,4返回指定键所映射的值;5如果此映射不包含该键的映射关系,则返回null。 6指定key值,7返回指定键所映射的值, 8keySet()9.返回此映射中包含的键的Set视图,10.values()11.返回此映射中包含的值的Collection视图。 12.entrySet()方法,13.返回此映射中包含的映射关系的Set视图。 11importjava.util.HashMap; importjava.util.Map; publicclassx{ publicstaticvoidmain(Stringargs[]){ Mapjjj1=newHashMap(); jjj1.put("1990","xide"); jjj1.put("1994","baxi"); jjj1.put("1998","faguo"); System.out.println("第一次测试"); Stringyear="2005"; System.out.println("输入变量为year,"+year); if(jjj1.containsKey(year)==true){System.out.println(jjj1.get(year));}else{System.out.println("没有举办世界杯。 ");} System.out.println("第二次测试"); year="1998"; System.out.println("输入变量为year,"+year); if(jjj1.containsKey(year)==true){System.out.println(jjj1.get(year));}else{System.out.println("没有举办世界杯。 ");} } } 12 importjava.util.HashMap; importjava.util.Iterator; importjava.util.Map; importjava.util.Map.Entry; publicclassx{ publicstaticvoidmain(Stringargs[]){ System.out.println("================="); System.out.println("第一次测试课程安排"); Map jjj1.put("老师","课程"); jjj1.put("Tom","CoreJava"); jjj1.put("John","Oracle"); jjj1.put("Susan","Oracle"); jjj1.put("Jerry","JDBC"); jjj1.put("Jim","Unix"); jjj1.put("kevin","JSP"); jjj1.put("Lucy","JSP"); System.out.println(jjj1.entrySet()); System.out.println("================="); System.out.println("第2次测试增加一个老师Allen教JDBC"); jjj1.put("Allen","JDBC"); System.out.print(jjj1.entrySet()); System.out.println("================="); System.out.println("第3次测试增加Lucy改为教CoreJava"); jjj1.put("Lucy","CoreJava"); System.out.print(jjj1.entrySet()); System.out.println("================="); System.out.println("第4次测试遍历Map,输出所有的老师及老师教授的课程"); System.out.print(jjj1.entrySet()); System.out.println("================="); System.out.println("第5次测试利用Map,输出所有教JSP的老师。 "); 1510 50 30 16A 17packageuser; publicclassAddrress{ Stringadrressname; StringzipCode; @Override publicStringtoString(){ return"[adrressname="+adrressname+",zipCode="+zipCode+"]"; } publicStringgetAdrressname(){ returnadrressname; } publicvoidsetAdrressname(Stringadrressname){ this.adrressname=adrressname; } publicStringgetZipCode(){ returnzipCode; } publicvoidsetZipCode(StringzipCode){ this.zipCode=zipCode; } } packageuser; importjava.util.*; publicclassWorker{ privateintage; privateStringname; privatedoublesalary; privateStringadress; Addrressadrress=newAddrress(); @Override publicStringtoString(){ returnname+"[age="+age+",name="+name+",salary="+salary+",adrress"+adrress+"]"; } publicWorker(){} publicWorker(Stringname,intage,doublesalary,Addrressadrress){ this.name=name; this.age=age; this.salary=salary; this.adrress=adrress; } publicintgetAge(){ returnage; } publicvoidsetAge(intage){ this.age=age; } publicStringgetName(){ returnname; } publicvoidsetName(Stringname){ this.name=name; } publicdoublegetSalary(){ returnsalary; } publicvoidsetSalary(doublesalary){ this.salary=salary; } publicvoidwork(){ System.out.println(getName()+"work");} @Override publicbooleanequals(Objectobj){ Workeruser1=newWorker(); user1=(Worker)obj; if(obj! =null){ //第二步进行比较属性值是否相等 returnthis.name.equals(user1.name)&&this.age==(user1.getAge()); } returntrue;} @Override publicinthashCode(){ intresult=0; if(name! =null){result=name.hashCode();} returnresult+age; //TODOAuto-generatedmethodstub //returnsuper.hashCode(); }} 18packageuser; importjava.util.HashMap; importjava.util.Map; publicclassfootball{ publicstaticvoidmain(Stringargs[]){ Mapjjj1=newHashMap(); jjj1.put("1990","xide"); jjj1.put("1994","baxi"); jjj1.put("2002","faguo"); jjj1.put("1998","faguo"); jjj1.put("2006","faguo"); jjj1.put("2010","faguo"); System.out.println("第一次测试"); Stringyear="2005"; System.out.println("输入变量为year,"+year); if(jjj1.containsKey(year)==true){System.out.println(jjj1.get(year));}else{System.out.println("没有举办世界杯。 ");} System.out.println("第二次测试"); year="1998"; System.out.println("输入变量为year,"+year); System.out.println(jjj1.get("henan"));//荷兰还没夺过冠. if(jjj1.containsKey(year)==true){System.out.println(jjj1.get(year));}else{System.out.println("没有举办世界杯。 ");} Stringqiudui="henan"; if(jjj1.containsValue(qiudui)==true){System.out.println(qiudui+"夺过冠");}else{System.out.println(qiudui+"未夺过世界杯。 ");} } } 19 packageuser; importjava.util.*; publicclassTestAccout{ publicstaticvoidmain(String[]args){ Listlist=newArrayList(); list.add(newAccount(10.00,"1234")); list.add(newAccount(15.00,"5678")); list.add(newAccount(0,"1010")); Mapjjj=newHashMap(); Accountaa=newAccount(); Listlist1=newArrayList(); for(inti=0;i jjj.put(list1,list); System.out.println(jjj.entrySet()); } } packageuser; publicclassAccount{ longID; doublebalance; Stringpassword; Account(){} Account(doublebalance,Stringpassword){this.balance=balance;this.password=password;} publiclonggetID(){ returnID; } publicvoi
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