java学习之路----java开发实战经典第12章习题及答案 - JAVA

< http://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">vcD4KPHA+PGltZyBzcmM9"https://www.cppentry.com/upload_files/article/76/1_55ste__.jpg" alt="\">

答案：

1. public class IOtest { public static void main(String[] args) { Scanner scanner= new Scanner(System. in); int a[]= new int[3]; int i=0; //boolean flage =true; while(i!=3){ a[i]=scanner.nextInt(); i++; } scanner.close(); Arrays. sort(a); System. out.println("最小" +a[0]+"------" +"最大" +a[2]); }
}
2. public class IOtest { public static void init(String name,String str) throws Exception { File file= new File("f:" +File. separator+name); if(!file.exists()){ file.createNewFile(); DataOutputStream out= new DataOutputStream( new FileOutputStream(file)); out.writeBytes(str); out.close(); } } public static void main(String[] args) throws Exception{ init("b.txt", "hello world"); }
}
3. public class IOtest { public static void main(String[] args) throws Exception{ Scanner scanner= new Scanner(System. in); int i=0; java.util.List list= new ArrayList (); while(i!=5){ list.add(scanner.next()); i++; } scanner.close(); for( int j=list.size();j>0;j--){ System. out.print(list.get(j-1)+"\t" ); } }
} 4. public class IOtest { public static void main(String[] args) throws Exception{ Scanner scanner= new Scanner(System. in); PrintStream print= new PrintStream( new File("f:" +File. separator +"a.txt" )); String str=scanner.next(); scanner.close(); String name= null ; String age= null ; String s[]= str.split( "[\\|]" ); Map map= new HashMap (); for (String s1:s){ String s2[] =s1.split( "[\\:]" ); for (String s3:s2){ if (s3.matches("\\d+" )){ age=s3; } else { name=s3; } map.put(name, age); } } List >ma= new ArrayList >(map.entrySet()); Collections. sort(ma, new Comparator >() {
@Override public int compare(Entry o1, Entry o2) {
if (o1.getValue()!= null&&o2.getValue()!= null&&(Integer. parseInt(o1.getValue())>=Integer. parseInt(o2.getValue()))){ return -1; } else { return 1; } } }); System. out .println(ma); // for(Map.Entry m:map.entrySet()){ // // } }
} 5. public class IOtest { public static void main(String[] args) throws Exception{ Scanner scanner= new Scanner(System. in); //PrintStream print=new PrintStream(new File("f:"+File.separator+"a.txt")); boolean Y= true ; String str= null ; while (Y){ str+=scanner.next(); System. out .println("是否继续输入" ); String s=scanner.next(); if (s.equalsIgnoreCase("Y" )){ Y= true ; System. out .println("请继续输入" ); } if (s.equalsIgnoreCase("N" )){ Y= false ; System. out .println("退出输入" ); } } String name= null ; String age= null ; DataOutputStream out= new DataOutputStream( new FileOutputStream( new File("f:" +File. separator+ "a.txt"))); out.writeBytes(str); out.close(); scanner.close(); String s[]= str.split( "[\\|]" ); Map map= new HashMap (); for (String s1:s){ String s2[] =s1.split( "[\\:]" ); for (String s3:s2){ if (s3.matches("\\d+" )){ age=s3; } else { name=s3; } map.put(name, age); } } List >ma= new ArrayList >(map.entrySet()); Collections. sort(ma, new Comparator >() {
@Override public int compare(Entry o1, Entry o2) {
if (o1.getValue()!= null&&o2.getValue()!= null&&(Integer. parseInt(o1.getValue())>=Integer. parseInt(o2.getValue()))){ return -1; } else { return 1; } } }); System. out .println(ma); // for(Map.Entry m:map.entrySet()){ // // } }
} 6. public class IOtest { public static void main(String[] args) throws Exception{ System. out .println("请输入一段数字字符串" ); Scanner scanner= new Scanner(System. in); String str=scanner.next(); scanner.close(); int a=0;//偶数 int b=0;//奇数 int sum=0; for ( int i=0;i if (sum%2==0){ a++; } else { b++; } } System. out .println("总数是：" +str.length()+ " 偶数："+a+ " 奇数:"+b); }
}

7. public class IOtest { public static void main(String[] args) throws Exception{ System. out .println("请输入用户名" ); Scanner scanner= new Scanner(System. in); String userName=scanner.next(); System. out .println("请输入密码" ); String password=scanner.next(); while (userName== null||password== null){ if (userName== null){ System. out .println("请输入用户名" ); userName=scanner.next(); } if (password== null){ System. out .println("请输入密码" ); password=scanner.next(); } } int count=0; while (userName!= null&&password!= null){ if (userName.equals("mldn" )&&password.equals( "hello")){ System. out .println("登陆成功" ); scanner.close(); return ; } else { count++; if (count==3){ System. out .println("连续登陆失败三次，系统推出" ); scanner.close(); return ; } else { System. out .println("连续登陆三次失败，则系统退出，您还有" +(3-count)+ "次"); System. out .println("用户名或密码错误，请重新输入：" ); System. out .println("请输入用户名" ); userName=scanner.next(); System. out .println("请输入密码" ); password=scanner.next(); } } } }
}
8. public class IOtest { public static void main(String[] args) throws Exception{ System. out .println("请输入源文件" ); Scanner scanner= new Scanner(System. in); String ypath=scanner.next(); System. out .println("请输入目标文件" ); String mbpath=scanner.next(); scanner.close(); OutputStream out= new FileOutputStream( new File(mbpath)); InputStream in= new FileInputStream( new File(ypath)); int temp=0; while ((temp=in.read())!=-1){ out.write(temp); } System. out .println("复制完成" ); out.close(); in.close(); }
}
10. class Student{ private int id ; private String name; private int count ;
public int getId() { return id ; }
public void setId( int id) { this .id = id; }
public String getName() { return name ; }
public void setName(String name) { this .name = name; }
public int getCount() { return count ; }
public void setCount( int count) { this .count = count; }
public Student( int id, String name, int count) { this .id = id; this .name = name; this .count = count; } }

public class IOtest { public static void main(String[] args) throws Exception{ Scanner scanner= new Scanner(System. in); Student student1= new Student(1,"张三" ,0); Student student2= new Student(2,"李四" ,0); Student student3= new Student(3,"王五" ,0); Student student4= new Student(4,"赵六" ,0); Student students[]={student1,student2,student3,student4}; for (Student student:students){ System. out .println(student.getId()+": "+student.getName()+ " 【"+student.getCount()+ "】" ); } int a=1; int num1=0,num2=0,num3=0,num4=0; while (a!=0){ String str= scanner.next(); if (str.matches("\\d+" )){ a=Integer. parseInt(str); System. out .println("请输入班长候选人代号(数字0结束)：" +a); if (a==0){ Map map= new HashMap (); for (Student student:students){ System. out .println(student.getId()+": "+student.getName()+ " 【"+student.getCount()+ "】" ); map.put(student.getName(), student.getCount()); } List >ma= new ArrayList >(map.entrySet()); Collections. sort(ma, new Comparator >() {
@Override public int compare(Entry o1, Entry o2) {
if (o1.getValue()!= null &&o2.getValue()!= null &&o1.getValue()>=o2.getValue()){ return 1; } else { return -1; } } }); System. out .println(ma.get(3).getKey()+"同学，最后以" +ma.get(3).getValue()+ "当选班长"); return ; } if (a==1){ num1++; students[a-1].setCount(num1); } else if (a==2){ num2++; students[a-1].setCount(num2); } else if (a==3){ num3++; students[a-1].setCount(num3); } else if (a==4){ num4++; students[a-1].setCount(num4); } else { System. out .println("此次选票无效，请输入正确的候选人代号" ); } } else { System. out .println("此次选票无效，请输入正确的候选人代号" ); System. out .println("请输入班长候选人代号(数字0结束)：" +str); } } }

}