作业第十四章

一简答题
1.根据目录结构myjava\practice1\Foo.java,写出Foo类的包名
答：包名为：myjava.practice1:
2.改写第12章中简答题第3题中的计算机类（Calculator)。要求将加减乘除的方法改成带参数的方法，再定义一个运算方法ope(),接收用户选择的运算和两个数字，根据用户选择的运算计算结果。
public class DJ14word2Calculator {
public double add(double num1,double num2){
System.out.print(num1+"+"+num2+"=");
return(num1+num2);
}
public double minus(double num1,double num2){
System.out.print(num1+"-"+num2+"=");
return(num1-num2);
}
public double multiple(double num1,double num2){
System.out.print(num1+""+num2+"=");
return(num1num2);
}
public double divide(double num1,double num2){
System.out.print(num1+"/"+num2+"=");
return(num1/num2);
}
public double ope(int op,double num1,double num2){
if(op1){
return add(num1,num2);
}else if(op2){
return minus(num1,num2);
}else if(op==3){
return multiple(num1,num2);
}else{
return divide(num1,num2);
}
}
}

import java.util.Scanner;
public class DJ14word2 {
@SuppressWarnings({ “resource” })
public static void main(String[] args) {
DJ14word2Calculator calc=new DJ14word2Calculator();
Scanner i=new Scanner(System.in);
System.out.print(“请选择运算:1.加法2.减法3.乘法4.除法:”);
int op=i.nextInt();
System.out.print(“请输入第一个数:”);
double num1=i.nextDouble();
System.out.print(“请输入第二个数:”);
double num2=i.nextDouble();
System.out.println(calc.ope(op,num1,num2));
}
}

3.模拟一个简单的购房商贷月供计算器，假设按照以下的公式计算总利息和每月还款金额
public class DJ14word3Loan {
public double loan(double loan,int yearchoice){
double money=0;
switch(yearchoice){
case 1:
money=loan1.0603/36;
System.out.println(“月供为:”+money);
break;
case 2:
money=loan1.0612/60;
System.out.println(“月供为:”+money);
break;
case 3:
money=loan*1.0639/240;
System.out.println(“月供为:”+money);
break;
default:
System.out.println(“请输入正确的数字!”);
break;
}
return money;
}
}

import java.util.Scanner;

public class DJ14word3 {
@SuppressWarnings({ “unused”, “resource” })
public static void main(String[] args) {
DJ14word3Loan l=new DJ14word3Loan();
Scanner i=new Scanner(System.in);
System.out.print(“请输入贷款金额:”);
double lloan=i.nextDouble();
System.out.print(“请输入贷款年限:1.3年(36个月)2.5年(60个月)3.20年(240个月)”);
int lyearchoice=i.nextInt();
}

4.根据指定不同的行及字符，生成不同的三角形。
public class DJ14word4Triangle {
public void printTriangle(int row,String ch){
for(int a=0;a<row;a++){
for(int b=0;b<=a;b++){
System.out.print(ch);
}
System.out.println();
}
}
}

import java.util.Scanner;

public class DJ14word4 {
@SuppressWarnings(“resource”)
public static void main(String[] args) {
DJ14word4Triangle l=new DJ14word4Triangle();
Scanner i=new Scanner(System.in);
System.out.print(“请输入行数:”);
int lrow=i.nextInt();
System.out.print(“请输入打印的字符:”);
String lch=i.next();
l.printTriangle(lrow,lch);
}
}

5.根据三角形的三条长。判断 其是直角，钝角，锐角，三角形。

public class DJ14word5Triangle {
public boolean it(int a,int b,int c){
boolean flag=false;
if((a+b)>c&&(a+c)>b&&(c+b)>a){
flag=true;
}
return flag;
}
public String shape(int a,int b,int c){
String shape="";
if(ab&&bc){
shape=“这是个等边三角形”;
}else if(ab||bc||ca){
shape=“这是个等腰三角形”;
}else if(aa+bbcc||aa+cc==bb||bb+cc==aa){
shape=“这是个直角三角形”;
}else if(aa+bb>cc||aa+cc>bb||bb+cc>aa){
shape=“这是个锐角三角形”;
}else if(aa+bb<cc||aa+cc<bb||bb+cc<a*a){
shape=“这是个钝角三角形”;
}
return shape;
}
}
import java.util.Scanner;

public class DJ14word5 {
@SuppressWarnings(“resource”)
public static void main(String[] args) {
DJ14word5Triangle l=new DJ14word5Triangle();
String answer="";
Scanner i=new Scanner(System.in);
do{
System.out.print(“请输入第1条边:”);
int a=i.nextInt();
System.out.print(“请输入第2条边:”);
int b=i.nextInt();
System.out.print(“请输入第3条边:”);
int c=i.nextInt();
if(l.it(a,b,c)){
System.out.println(l.shape(a,b,c));
}else{
System.out.println(“这不能构成三角形”);
}
System.out.print(“继续吗?(y/n):”);
answer=i.next();
}while(“y”.equals(answer));
System.out.println(“谢谢使用!”);
}
}
6.编写程序，向整型数组的指定位置插入元素，并输出插入前后数组的值。
public class DJ14word6ia {
public void insertArray(int[] arr,int index,int value){
for(int a=arr.length-1;a>=index;a–){
arr[a]=arr[a-1]; //向后移一位
}
arr[index-1]=value; //赋值
}
}

public class DJ14word6 {
public static void main(String[] args) {
int[] a=new int[20]; //定义一个新数组
a[0]=45;
a[1]=12;
a[2]=0;
a[3]=87;
a[4]=21;
a[5]=1;
a[6]=89;
a[7]=123;
a[8]=21;
System.out.println(“插入前:”);
for(int i=0;i<a.length-1;i++){
System.out.print(a[i]+" “);
}
DJ14word6ia ia=new DJ14word6ia(); //引用另一页
ia.insertArray(a,3,10); //赋值
System.out.println(”\n插入后:");
for(int i=0;i<a.length-1;i++){
System.out.print(a[i]+" ");
}
}
}
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7.本学期期末学员共参加了三门课，即Java、C、SQL,编写方法计算每位学员三门课的平均分。
public class DJ14word7student {
public int java;
public int C;
public int SQL;
}
public class DJ14word7studentBiz {
public double getAvg(DJ14word7student stu){
return (stu.java+stu.C+stu.SQL)/3;
}
}
import java.util.Scanner;
public class DJ14word7 {
@SuppressWarnings(“resource”)
public static void main(String[] args) {
DJ14word7student curriculum=new DJ14word7student();
Scanner i=new Scanner(System.in);
System.out.print(“请输入你的java成绩:”);
curriculum.java=i.nextInt();
System.out.print(“请输入你的C成绩:”);
curriculum.C=i.nextInt();
System.out.print(“请输入你的SQL成绩:”);
curriculum.SQL=i.nextInt();
DJ14word7studentBiz calculation=new DJ14word7studentBiz();
double avg=calculation.getAvg(curriculum);
System.out.println(“你的平均分是:”+avg);
}
}