标签：java
*4.21(计算不同利率下的贷款)编写程序，让用户输入贷款总额及以年为单位的贷款期限，以1/8为递增量，显示从5%到8%的利率下每月支付额和总偿还额。假设输入贷款总量为10 000，还贷期限为5年，所显示的输出如下:
贷款总额:to 000
年数:5
利率月支付额总偿还额
5%188 .71 11322.74
5 .125%189.28 11357.13
5 .25%189.85 11391.59
...
//Exercise3_26.java: displays the monthly and total payments
//for each interest rate starting from 5% to 8%,
//with an incremental of 1/8.
import javax.swing.JOptionPane;
public class Exercise3_26 {
// Main method
public static void main(String[] args) {
int numOfYears;
double loanAmount;
// Enter number of years
String numOfYearsString = JOptionPane.showInputDialog(null,
"Enter number of years as an integer, \nfor example 5:",
"Exercise3_26 Input", JOptionPane.QUESTION_MESSAGE);
// Convert string to int
numOfYears = Integer.parseInt(numOfYearsString);
// Enter loan amount
String loanString = JOptionPane.showInputDialog(null,
"Enter loan amount, for example 120000.95:",
"Exercise3_26 Input", JOptionPane.QUESTION_MESSAGE);
// Convert string to double
loanAmount = Double.parseDouble(loanString);
// Display the header
System.out.print("Interest Rate");
System.out.print("\t" + "Monthly Payment");
System.out.println("\t\t" + "Total Payment");
double monthlyInterestRate;
double monthlyPayment;
double totalPayment;
for (double annualInterestRate = 5.0; annualInterestRate <= 8.0;
annualInterestRate += 1.0 / 8) {
// Obtain monthly interest rate
monthlyInterestRate = annualInterestRate / 1200;
// Compute mortgage
monthlyPayment = loanAmount*monthlyInterestRate/
(1 - (Math.pow(1 / (1 + monthlyInterestRate), numOfYears * 12)));
totalPayment = monthlyPayment * numOfYears * 12;
// Display results
System.out.print(annualInterestRate + "%");
System.out.print("\t\t" + (int)(monthlyPayment * 100) / 100.0);
System.out.println("\t\t\t" + (int)(totalPayment * 100) / 100.0);
}
}
}**4.22(显示分期还贷时间表)对于给定的贷款额、月支付额包括偿还本金及利息。月利息是通过月利
率乘以余额(剩余本金)计算出来的。因此，每月偿还的本金等于月支付额减去月利息。编写一个程序，让用户输入贷款总额、贷款年数及利率，而后显示分期还贷时间表。假设输入的贷款总额为10 000，还贷期限为1年，年利率为7%，显示如下的表格:
贷款总额:10 000
年数:1
年利率:7%
月支付额:865.26
总偿还额：
10383.21
月份 利息 本金 余额
1 58.33 806.93 9193.07
2 53.62 811.64 8381.43
...
1 1 10.0 855.26 860.27
1 2 5.01 860.25 0.01
注:最后一次偿还后，余额可能不为0。如果是这样的话，最后一个月支付额应当是正常的月支付额加上最后的余额。
提示编写一个循环来打印该表。由于每个月的还贷额都是相同的，因此，应当在循环之前将其计算出来。开始时，余额即为贷款总额。在循环的每次迭代中，计算利息及本金，并更新余额。这个循环可以这样:
for (i =1;i <= numberOfYears * 12;i++) {
interest = monthlyInterestRate * balance;
principal = monthlyPayment - interest;
balance = balance - principal;
System.out.println(i + "\t\t" +interest
+ "\t\t" + principal +"\t\t" + balance);
}
import javax.swing.JOptionPane;
public class Exercise3_27 {
public static void main(String[] args) {
int numOfYears;
double loanAmount;
// Enter yearly interest rate
String annualIntrestRateString = JOptionPane.showInputDialog(
"Enter yearly interest rate, for example 8.25:");
// Convert string to double
double annualInterestRate =
Double.parseDouble(annualIntrestRateString);
// Obtain monthly interest rate
double monthlyInterestRate = annualInterestRate/1200;
// Enter number of years
String numOfYearsString = JOptionPane.showInputDialog(
"Enter number of years as an integer, \nfor example 5:");
// Convert string to int
numOfYears = Integer.parseInt(numOfYearsString);
// Enter loan amount
String loanString = JOptionPane.showInputDialog(
"Enter loan amount, for example 120000.95:");
// Convert string to double
loanAmount = Double.parseDouble(loanString);
// Compute mortgage
double monthlyPayment = loanAmount*monthlyInterestRate /
(1 - (Math.pow(1 / (1 + monthlyInterestRate), numOfYears * 12)));
double balance = loanAmount;
double interest;
double principal;
System.out.println("Loan Amount: " + loanAmount);
System.out.println("Number of Years: " + numOfYears);
System.out.println("Interest Rate: " + annualInterestRate + "%");
System.out.println();
System.out.println("Monthly Payment: " + (int)(monthlyPayment * 100) / 100.0 );
System.out.println("Total Payment: " + (int)(monthlyPayment * 12 * numOfYears * 100) / 100.0 + "\n" );
// Display the header
System.out.println("Payment#\tInterest\tPrincipal\tBalance");
int i;
for (i = 1; i <= numOfYears * 12; i++) {
interest = (int)(monthlyInterestRate * balance * 100) / 100.0;
principal = (int)((monthlyPayment - interest) * 100) / 100.0;
balance = (int)((balance - principal) * 100) / 100.0;
System.out.println(i + "\t\t" + interest
+ "\t\t" + principal + "\t\t" + balance);
}
}
}近似计算π
π = 4 * （1 - 1/3 + 1/5 - 1/7 + 1/9 -...- 1/(2i - 1) + 1/(2i + 1)
public class Exercise3_30 {
public static void main(String[] args) {
double pi = 0;
double term;
int sign = 1;
for (int i = 1; i <= 100000; i++) {
term = sign * 4.0 / (2 * i - 1);
pi += term;
sign = -1 * sign;
if (i == 10000 || i == 20000 || i == 30000 || i == 40000 ||
i == 50000 || i == 60000 || i == 70000 || i == 80000 ||
i == 90000 || i == 100000)
System.out.println("The PI is " + pi + " for i = " + i);
}
}
}近似计算e
e = 1 + 1/1! + 1/2! + 1/3!+ ...+ 1/i!
新的一项item由前面一个item除以i得到
public class Exercise3_31 {
public static void main(String[] args) {
double e = 1;
double item = 1;
for (int i = 1; i <= 100000; i++) {
item = item / i;
e += item;
if (i == 10000 || i == 20000 || i == 30000 || i == 40000 ||
i == 50000 || i == 60000 || i == 70000 || i == 80000 ||
i == 90000 || i == 100000)
System.out.println("The e is " + e + " for i = " + i);
}
}
}Java语言程序设计基础篇 循环（四）练习,布布扣,bubuko.com
标签：java
原文地址：http://coolview.blog.51cto.com/7138551/1408129
