二、编程题
1 将数组 int [] a={9,5,7,8,1,3,2,6,4} 进行冒泡排序
Public class test {
Public static void main(String[] args){
int [] a={9,5,7,8,1,3,2,6,4};
for(int i=1;i<a.length;i++){
for(int j=0;j<a.length-i;j++){
if(a[j]<a[j+1]){
int temp=a[j];
a[j]=a[j+1];
a[j+1]=temp;
}
}
2 写出单例设计模式
Public class Singleton{
Private Singleton(){}
Private static Singleton instance=null;
Public static Singleton getInstance(){
If(instance==null){
Instance=new Singleton();
}
return instance;
}
}
3 键盘输入十行数据，直到输入quit就退出程序，将输入的数据保存在D:\temp\info.txt中，该文件不存在就创建该文件。
Public class Test{
static String path=” D:\\temp\\info.txt”;
Public static void main(String[] args){
File f=new File(path);
If( ! f.exists() ){
f.createNewFile();
}
BufferedReader br=new BufferedReader(New InputStreamReader(System.in));
BufferedWriter bw=new BufferedWriter(new FileWriter(f));
String line=null;
While((line=br.readLine())!=null &&!(line.equals(“quit”))){
bw.write(line);
bw.newLine();
bw.flush();
}
br.close();
bw.close();
}
}
4 模拟生成1个班级,该班级有9个学生对象，用集合模拟下列操作。
A.班级再增加一位学生
B.将学号是S001的姓名修改为”张恒”
C.统计所有学生的平均分
D.将学生的所有信息保存到文件student.txt中
}
for(int k:a){
system.out.print(k+” ”);
}
Public class Student{
Private String sno;
Private String name;
Private int score;
Public String toSTring(){
Return “Student [sno=”+sno+”, name=”+name+”, score=”+score+”]”;
}
Public Student(String sno,String name,int score){
This.sno=sno;
This.name=name;
This.score=score;
}
Public void setScore(int score){
This.score=score;
}
Public int getScore(){
Return score;
}
Public void setSno(String sno){
This.sno=sno;
}
Public String getSno(){
Return sno;
}
Public void setName(String name){
This.name=name;
}
Public String getName(){
Return name;
}
Public static void main(String[] args){
List<Student> class="new" ArrayList<Student>();
Student students={
New Student(“s001”,”张1”,65);
New Student(“s001”,”张2”,66);
New Student(“s001”,”张3”,67);
New Student(“s001”,”张4”,68);
New Student(“s001”,”张5”,44);
New Student(“s001”,”张6”,55);
New Student(“s001”,”张7”,66);
};
For(Student student :students){
Class.add(student);
}
Class.add(new Student(“s008”,”张8”,88));
For(Student student :students){
If(student.sno.equals(“s001”)){
Student.setName(“张恒”);
Break;
}
}
Int total=0,i=0;
For(Student student :students){
Total+=student.getsScore();
i++;
}
System.out.print(“平均分”+total/i);
File f=new File(“f: \\student.txt”);
File f=new File(path);
If( ! f.exists() ){
f.createNewFile();
}
BufferedWriter bw=new BufferedWriter(new FileWriter(f,true));
For(Student student :students){
Bw.write(student.toString());
}
Bw.close();
}
}
5 模拟四个线程对同一个数据I进行操作
1号和3号线程做加一
2号和4号线程做减一
}
Public class Date{
Static int index=0;
Public synchronized void add(){
Index++;
}
Public synchronized void sub(){
Index--;
}
}
Public class A implements Runnable{
Date date;
Public A(Date date){
This.date=date;
}
Public void run(){
For(int i=0;i<20;i++){
date.add();
Thread.sleep(20);
}
}
}
Public class B implements Runnable{
Date date;
Public B(Date date){
This.date=date;
}
Public void run(){
For(int i=0;i<20;i++){
date.sub();
Thread.sleep(30);
}
}
}
Public class Test{
Public static void main(String[] args){
Date date =new Date();
A a=new A(date);
B b=new B(date);
Thread t1=new Thread(a,”1号”);
Thread t3=new Thread(a,”3号”);
Thread t1=new Thread(b,”2号”);
Thread t1=new Thread(b,”4号”);
t1.start();
t2.start();
t3.start();
t4.start();
}
}
