java异常处理
编写一个NewLoan类，使满足以下要求：如果年利率（AnnualInterestRate，AIR）、年数（NumOfYears，NOY）或贷款总额（LoanAmount，LA）任意一项小于或等于零，则抛出IllegalArgumentException异常，若有多项不符合要求，则以最前项为准，输出格式见范例；
如果数据均符合要求，构造printTotalPayment()方法，返回总额，结果保留3位小数。
输入格式:
输入有多组数据，一个实数表示年利率，一个整数表示年数，一个实数表示贷款总额。
输出格式:
若任意一项小于或等于零，抛出IllegalArgumentException异常及相应描述（Annual interest rate must be positive.或Number of years must be positive.或Loan amount must be positive.）；
有多项不符合，以不符合最前项为准；
若均符合要求，按照格式输出总额。
输入样例：
1 1 1000
2.5 0 2000
0 0 0
输出样例：
totalPayment is 1005.424
java.lang.IllegalArgumentException: Number of years must be positive.
java.lang.IllegalArgumentException: Annual interest rate must be positive.
下面是我写的代码
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
while (input.hasNext()) {
double AIR = input.nextDouble();
int NOY = input.nextInt();
double LA = input.nextDouble();
try {
NewLoan m = new NewLoan(AIR, NOY, LA);
System.out.printf(m.printTotalPayment());
System.out.printf("\n");
} catch (Exception ex) {
System.out.println(ex);
}
}
}
}
/* 请在这里填写答案 */
class NewLoan{
double a,c;
int b;
NewLoan(double air,int noy,double la) throws IllegalArgumentException {
this.a=air;//年利率
this.b=noy;//年数
this.c=la;//贷款额
judge();
}
public void judge() throws IllegalArgumentException{
if(this.a<=0||(this.a<=0&&this.b<=0&&this.c<=0)){
throw new java.lang.IllegalArgumentException("Annual interest rate must be positive.");
}
else if(this.b<=0){
throw new java.lang.IllegalArgumentException("Number of years must be positive.");
}
else if(this.c<=0){
throw new java.lang.IllegalArgumentException("Loan amount must be positive.");
}
}
String printTotalPayment(){
double sum=((this.a/1200.0)/(1-(1/Math.pow(1+this.a/1200.0,12))))*12.0*this.c*this.b;
return "totalPayment is "+String.format("%.3f",sum);
}
}
class IllegalArgumentException extends Exception{
String r;
IllegalArgumentException(String r){
this.r=r;
}
@Override
public String getMessage() {
return this.r;
}
}
代码中存在以下问题：
1. 在NewLoan类的构造方法中，只是调用了judge()方法进行判断，但没有在该方法中抛出异常。应该在judge()方法中使用if条件判断，当满足条件时，抛出IllegalArgumentException异常。
2. 在Main类的main方法中，使用了错误的方法签名，应该使用String[] args而不是String args。
下面是修改后的代码：
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
while (input.hasNext()) {
double AIR = input.nextDouble();
int NOY = input.nextInt();
double LA = input.nextDouble();
try {
NewLoan m = new NewLoan(AIR, NOY, LA);
System.out.printf(m.printTotalPayment());
System.out.printf("\n");
} catch (IllegalArgumentException ex) {
System.out.println(ex.getMessage());
}
}
}
}
class NewLoan {
private double AIR;
private int NOY;
private double LA;
NewLoan(double air, int noy, double la) throws IllegalArgumentException {
this.AIR = air;
this.NOY = noy;
this.LA = la;
judge();
}
public void judge() throws IllegalArgumentException {
if (this.AIR <= 0) {
throw new IllegalArgumentException("Annual interest rate must be positive.");
}
if (this.NOY <= 0) {
throw new IllegalArgumentException("Number of years must be positive.");
}
if (this.LA <= 0) {
throw new IllegalArgumentException("Loan amount must be positive.");
}
}
public String printTotalPayment() {
double totalPayment = LA * Math.pow(1 + AIR / 100, NOY);
return "totalPayment is " + String.format("%.3f", totalPayment);
}
}
以上代码中，使用了私有变量来存储输入的年利率、年数和贷款总额，在judge()方法中进行判断，并抛出异常。printTotalPayment()方法计算总额，并返回格式化后的字符串。在Main类的main方法中，通过try-catch语句捕获异常并输出相应信息。
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