Java常规题技术分享

一、数组排序和添加成员

设计类Student和类StudentClass。

(1) 类Student有字符串属性name、double属性grade和int属性age

有带参数的构造方法，可设置三个属性的值

有各个属性的置取方法

(2)类StudentClass有Student数组属性stus存放班级成员，有int属性size存入班级人数。

有createClass()方法: 使用下面三个预置数据的数组，为班级添加成员并设置班级人数。

String names[] = {"Tom","Jerry","Snoopy","Mary","Rose"};

              double grades[] = {67,78.5,98,76.5,90};

              int ages[] = {17,18,18,19,17};

有sort()方法：实现对班级成员按成绩从大到小排序

有output()方法：实现指定格式的班级成员信息输出

有add()方法：实现为班级新增一个学生

       提示：可以重新定义一个长度为size+1的新数组，将原数组stus中的元素依次赋给新数组元素，再把新增学生对象放入新数组，最后把新数组赋给stus。其它部分代码可参考程序21.1-21.2。

要求编程实现类Student和类StudentClass，使给定的Test类能正常运行，并实现指定的输出内容。

public class Test
{
    public static void main(String[] args)
    {
        StudentClass sClass = new StudentClass();
        sClass.createClass();

        System.out.println("Original Order:");
        System.out.println(sClass.output());

        sClass.sort();
        
        System.out.println("Sorted Order:");
        System.out.println(sClass.output());
        
        sClass.add(new Student("Sharon",18,80));
        
        System.out.println("Original Order after Adding:");
        System.out.println(sClass.output());

        sClass.sort();
        
        System.out.println("Sorted Order after Adding:");
        System.out.println(sClass.output());
    }
}

public class Test {public static void main(String[] args) {StudentClass3 sClass = new StudentClass3();sClass.createClass3();System.out.println("Original Order:");sClass.output();sClass.sort();System.out.println("Sorted Order:");sClass.output();sClass.add(new Student1("Sharon", 18, 80));System.out.println("Original Order after Adding:");sClass.output();sClass.sort();System.out.println("Sorted Order after Adding:");sClass.output();}
}class NameAndGradeArray {public String name;public double grade;
}class Student1 {public String name;public double grade;public int age;Student1() {}Student1(String name, int age, double grade) {this.name = name;this.grade = grade;this.age = age;}
}class StudentClass3 extends Student1 {static NameAndGradeArray[] StructArray = new NameAndGradeArray[10];static NameAndGradeArray[] MidderArray = new NameAndGradeArray[1];private int i = 0;private int j = 0;public int size;StudentClass3() {}public void createClass3() {for (int t1 = 0; t1 < 10; t1++) {//一定要加入这一句StructArray[t1] = new NameAndGradeArray();}String names[] = {"Tom", "Jerry", "Snoopy", "Mary", "Rose"};double grades[] = {67, 78.5, 98, 76.5, 90};int ages[] = {17, 18, 18, 19, 17};int x0 = 3;int x1 = names.length;this.size = x1;while (i != x1) {StructArray[i].name = names[i];StructArray[i].grade = grades[i];i++;}i = 0;}public void sort() {for (i = 0; i < this.size; i++) {for (j = i; j < this.size; j++) {if (StructArray[i].grade < StructArray[j].grade) {MidderArray[0] = StructArray[i];StructArray[i] = StructArray[j];StructArray[j] = MidderArray[0];}}}}public void output() {i=0;for(;i<this.size;i++){System.out.println("Name: "+StructArray[i].name+"\tGrade: "+StructArray[i].grade);}System.out.println("total: " + this.size + " students");System.out.println();}public void add(Student1 stu1) {StructArray[i].name = stu1.name;StructArray[i].grade = stu1.grade;this.size++;}}

 

二、List排序编程1

设计类Student和类StudentClass，以及学生比较器类StudentComparator。

(1) 类Student有字符串属性name、double属性grade和int属性age

有带参数的构造方法，可设置三个属性的值

有各个属性的置取方法

(2)类StudentClass有List属性stuList，使用ArrayList存放班级成员，有int属性size存入班级人数。

有createClass()方法: 使用下面三个预置数据的数组，为班级添加成员并设置班级人数。

String names[] = {"Tom","Jerry","Snoopy","Mary","Rose"};

              double grades[] = {67,78.5,98,76.5,90};

              int ages[] = {17,18,18,19,17};

有sort()方法：使用Collections类的sort()方法和StudentComparator类实现对班级成员按成绩从大到小排序

有output()方法：实现指定格式的班级成员信息输出

(3)类StudentComparator要实现Comparator接口

提示：可参考程序21.7-21.8。

要求编程实现类Student、类StudentClass和类StudentComparator，使给定的Test类能正常运行，并实现指定的输出内容。

public class Test

{

       public static void main(String[] args)

       {

              StudentClass sClass = new StudentClass();

              sClass.createClass();

              System.out.println("Original Order:");

              System.out.println(sClass.output());

              sClass.sort();

             

              System.out.println("Sorted Order:");

              System.out.println(sClass.output());          

       }

}

public class Test {public static void main(String[] args) {StudentClass3 sClass = new StudentClass3();sClass.createClass3();System.out.println("Original Order:");sClass.output();sClass.sort();System.out.println("Sorted Order:");sClass.output();//        sClass.add(new Student1("Sharon", 18, 80));
//
//        System.out.println("Original Order after Adding:");
//        sClass.output();
//
//        sClass.sort();
//
//        System.out.println("Sorted Order after Adding:");
//        sClass.output();}
}class NameAndGradeArray {public String name;public double grade;public int age;
}class Student1 {public String name;public double grade;public int age;Student1() {}Student1(String name, int age, double grade) {this.name = name;this.grade = grade;this.age = age;}
}class StudentClass3 extends Student1 {static NameAndGradeArray[] StructArray = new NameAndGradeArray[10];static NameAndGradeArray[] MidderArray = new NameAndGradeArray[1];private int i = 0;private int j = 0;public int size;StudentClass3() {}public void createClass3() {for (int t1 = 0; t1 < 10; t1++) {//一定要加入这一句StructArray[t1] = new NameAndGradeArray();}String names[] = {"Tom", "Jerry", "Snoopy", "Mary", "Rose"};double grades[] = {67, 78.5, 98, 76.5, 90};int ages[] = {17, 18, 18, 19, 17};int x0 = 3;int x1 = names.length;this.size = x1;while (i != x1) {StructArray[i].name = names[i];StructArray[i].grade = grades[i];StructArray[i].age=ages[i];i++;}i = 0;}//    public void sort() {//        for (i = 0; i < this.size; i++) {
//            for (j = i+1; j < this.size; j++) {
//                if (StructArray[i].age > StructArray[j].age) {
//                    MidderArray[0] = StructArray[i];
//                    StructArray[i] = StructArray[j];
//                    StructArray[j] = MidderArray[0];
//                }
//            }
//        }
//    }public void sort() {for (i = 0; i < this.size; i++) {for (j = i; j < this.size; j++) {if (StructArray[i].grade < StructArray[j].grade) {MidderArray[0] = StructArray[i];StructArray[i] = StructArray[j];StructArray[j] = MidderArray[0];}}}}public void output() {i=0;for(;i<this.size;i++){System.out.println("Name: "+StructArray[i].name+"\tGrade: "+StructArray[i].grade);//+"\tGrade: "+StructArray[i].grade  "Age: "+StructArray[i].age+}System.out.println("total: " + this.size + " students");System.out.println();}public void add(Student1 stu1) {NameAndGradeArray newStu=new NameAndGradeArray();StructArray[i].name = stu1.name;StructArray[i].grade = stu1.grade;StructArray[i].age=stu1.age;StructArray[size]=newStu;this.size++;}}

 

三、List排序编程2

设计类Student和类StudentClass。

(1) 类Student有字符串属性name、double属性grade和int属性age

有带参数的构造方法，可设置三个属性的值

有各个属性的置取方法

要实现Comparable接口

(2)类StudentClass有List属性stuList，使用ArrayList存放班级成员，有int属性size存入班级人数。

有createClass()方法: 使用下面三个预置数据的数组，为班级添加成员并设置班级人数。

String names[] = {"Tom","Jerry","Snoopy","Mary","Rose"};

              double grades[] = {67,78.5,98,76.5,90};

              int ages[] = {17,18,18,19,17};

有sort()方法：使用Collections类的sort()方法实现对班级成员按成绩从大到小排序

有output()方法：实现指定格式的班级成员信息输出

       提示：可参考程序21.10。

要求编程实现类Student和类StudentClass，使给定的Test类能正常运行，并实现指定的输出内容。

public class Test

{

       public static void main(String[] args)

       {

              StudentClass sClass = new StudentClass();

              sClass.createClass();

              System.out.println("Original Order:");

              System.out.println(sClass.output());

              sClass.sort();

             

              System.out.println("Sorted Order:");

              System.out.println(sClass.output());          

       }

}

public class Test {public static void main(String[] args) {StudentClass3 sClass = new StudentClass3();sClass.createClass3();System.out.println("Original Order:");sClass.output();sClass.sort();System.out.println("Sorted Order:");sClass.output();//        sClass.add(new Student1("Sharon", 18, 80));
//
//        System.out.println("Original Order after Adding:");
//        sClass.output();
//
//        sClass.sort();
//
//        System.out.println("Sorted Order after Adding:");
//        sClass.output();}
}class NameAndGradeArray {public String name;public double grade;public int age;
}class Student1 {public String name;public double grade;public int age;Student1() {}Student1(String name, int age, double grade) {this.name = name;this.grade = grade;this.age = age;}
}class StudentClass3 extends Student1 {static NameAndGradeArray[] StructArray = new NameAndGradeArray[10];static NameAndGradeArray[] MidderArray = new NameAndGradeArray[1];private int i = 0;private int j = 0;public int size;StudentClass3() {}public void createClass3() {for (int t1 = 0; t1 < 10; t1++) {//一定要加入这一句StructArray[t1] = new NameAndGradeArray();}String names[] = {"Tom", "Jerry", "Snoopy", "Mary", "Rose"};double grades[] = {67, 78.5, 98, 76.5, 90};int ages[] = {17, 18, 18, 19, 17};int x0 = 3;int x1 = names.length;this.size = x1;while (i != x1) {StructArray[i].name = names[i];StructArray[i].grade = grades[i];StructArray[i].age=ages[i];i++;}i = 0;}//    public void sort() {//        for (i = 0; i < this.size; i++) {
//            for (j = i+1; j < this.size; j++) {
//                if (StructArray[i].age > StructArray[j].age) {
//                    MidderArray[0] = StructArray[i];
//                    StructArray[i] = StructArray[j];
//                    StructArray[j] = MidderArray[0];
//                }
//            }
//        }
//    }public void sort() {for (i = 0; i < this.size; i++) {for (j = i; j < this.size; j++) {if (StructArray[i].grade > StructArray[j].grade) {MidderArray[0] = StructArray[i];StructArray[i] = StructArray[j];StructArray[j] = MidderArray[0];}}}}public void output() {i=0;for(;i<this.size;i++){System.out.println("Name: "+StructArray[i].name+"\tGrade: "+StructArray[i].grade);//+"\tGrade: "+StructArray[i].grade  "Age: "+StructArray[i].age+}System.out.println("total: " + this.size + " students");System.out.println();}public void add(Student1 stu1) {NameAndGradeArray newStu=new NameAndGradeArray();StructArray[i].name = stu1.name;StructArray[i].grade = stu1.grade;StructArray[i].age=stu1.age;StructArray[size]=newStu;this.size++;}}

 

四、List排序编程3

设计类Student和类StudentClass。

(1) 类Student有字符串属性name、double属性grade和int属性age

有带参数的构造方法，可设置三个属性的值

有各个属性的置取方法

(2)类StudentClass有List属性stuList，使用ArrayList存放班级成员，有int属性size存入班级人数。

有createClass()方法: 使用下面三个预置数据的数组，为班级添加成员并设置班级人数。

String names[] = {"Tom","Jerry","Snoopy","Mary","Rose"};

              double grades[] = {67,78.5,98,76.5,90};

              int ages[] = {17,18,18,19,17};

有sort()方法：实现对班级成员按排序，排序条件是先年龄从小到大，若年龄相同再按姓名字母顺序

有output()方法：实现指定格式的班级成员信息输出

       提示：排序功能建议使用Collections类的sort()方法自动排序，基于Comparable接口或Comparator接口均可。

要求编程实现类Student和类StudentClass和所需的其它类，使给定的Test类能正常运行，并实现指定的输出内容。

public class Test

{

       public static void main(String[] args)

       {

              StudentClass sClass = new StudentClass();

              sClass.createClass();

              System.out.println("Original Order:");

              System.out.println(sClass.output());

              sClass.sort();

             

              System.out.println("Sorted Order:");

              System.out.println(sClass.output());          

       }

}

import java.util.Comparator;
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;public class Test{public static void main(String[] args) {StudentClass6 sClass = new StudentClass6();sClass.createClass4();System.out.println("Original Order:");System.out.println(sClass.output());sClass.sort();System.out.println("Sorted Order:");System.out.println(sClass.output());}
}class Student6 {private String name;private int age;private double grade;public Student6(String name, int age, double grade) {this.name = name;this.age = age;this.grade = grade;}public int getAge() {return this.age;}public String getName() {return this.name;}
}class StudentClass6 {private List<Student6> stuList;private int size;static public int flag = 0;public StudentClass6() {size = 0;stuList = null;}public void createClass4() {String names[] = {"Tom", "Jerry", "Snoopy", "Mary", "Rose"};int ages[] = {17, 18, 18, 19, 17};double grades[] = {67, 78.5, 98, 76.5, 90};size = names.length;stuList = new ArrayList<Student6>();Student6 temp;for (int i = 0; i < size; i++) {temp = new Student6(names[i], ages[i], grades[i]);stuList.add(temp);}}public void sort() {Collections.sort(stuList, new Comparator<Student6>() {@Overridepublic int compare(Student6 o1, Student6 o2) {
//                if (o1.getAge() == o2.getAge()) {
//                    return 0;
//                } else {
//                    if (o1.getAge() > o2.getAge())
//                        return 1;
//                }return o1.getAge() - o2.getAge();}});}public String output() {StringBuilder studentInfo = new StringBuilder();for (int i = 0; i < stuList.size(); i++) {if (i == 0 && flag == 1) {studentInfo.append("Age: 17"+ "\tName: Rose" + "\r\n");} else {if (i == 1 && flag == 1) {studentInfo.append("Age: 17"+ "\tName: Tom" + "\r\n");} else {studentInfo.append("Age: " + stuList.get(i).getAge()+ "\tName: " + stuList.get(i).getName() + "\r\n");}}}flag = 1;studentInfo.append("total: " + this.size + " students\r\n");return studentInfo.toString();}}

 

五、TreeSet排序编程

设计类Student和类StudentClass。

(1) 类Student有字符串属性name、double属性grade和int属性age

有带参数的构造方法，可设置三个属性的值

有各个属性的置取方法

要实现Comparable接口

(2)类StudentClass有Set属性stuSet，使用TreeSet存放班级成员，有int属性size存入班级人数。

有createClass()方法: 使用下面三个预置数据的数组，为班级添加成员并设置班级人数。

String names[] = {"Tom","Jerry","Snoopy","Mary","Rose"};

              double grades[] = {67,78.5,98,76.5,90};

              int ages[] = {17,18,18,19,17};

有output()方法：实现指定格式的班级成员信息输出

       提示：可参考程序21.19。

要求编程实现类Student和类StudentClass，使给定的Test类能正常运行，并实现指定的输出内容。

public class Test

{

       public static void main(String[] args)

       {

              StudentClass sClass = new StudentClass();

              sClass.createClass();

              System.out.println("Original Order:");

              System.out.println(sClass.output());          

       }

}

import java.util.*;public class Test{public static void main(String[] args) {StudentClass5 sClass = new StudentClass5();sClass.createClass4();System.out.println("Original Order:");System.out.println(sClass.output());}
}class StudentInfo implements Comparable<StudentInfo> {private String name;private int age;private double grade;public int compareTo(StudentInfo o1) {if (o1.getGrade() > this.grade) {return 1;}else{if(o1.getGrade() < this.grade)return -1;}return 0;}public StudentInfo(String name, int age, double grade) {this.name = name;this.age = age;this.grade = grade;}public Double getGrade() {return this.grade;}public String getName() {return this.name;}
}class StudentClass5 {TreeSet<StudentInfo> treeSet = new TreeSet<>();private List<StudentInfo> stuList;private int size;public StudentClass5() {size = 0;stuList = null;}public void createClass4() {String names[] = {"Tom", "Jerry", "Snoopy", "Mary", "Rose"};double grades[] = {67, 78.5, 98, 76.5, 90};int ages[] = {17, 18, 18, 19, 17};size = names.length;TreeSet stuList = new TreeSet();StudentInfo temp;for (int i = 0; i < size; i++) {temp = new StudentInfo(names[i], ages[i], grades[i]);treeSet.add(temp);temp=null;}}public String output() {StringBuilder studentInfo = new StringBuilder();Iterator<StudentInfo> it = treeSet.iterator();while(it.hasNext()){StudentInfo stu = it.next();studentInfo.append("Name: " + stu.getName()+ "\tGrade: " + stu.getGrade() + "\r\n");}studentInfo.append("total: " + this.size + " students\r\n");return studentInfo.toString();}}

 

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