Question

奥凯,我仍然对贾瓦有新鲜事,我正走到这一 st的第九周。我将从一个学校项目上张贴一些来源代码——这是整个来源的NOT——这部法律是我摊还贷款的空档。我试图从菜单选择(向文字领域打印)或用户投入中摊销。问题在于,如果是数学,还是我的住所,那么我就不能说贷款没有适当摊销。我只想知道,任何人是否看到我所忽略的一点显而易见,如果是,请指出这一点,我就可以走上正确的轨道? 提前感谢!

来源:

private void amortizeButtonActionPerformed( java.awt.event.ActionEvent evt ) {
  // This module borrowed from Ryan Jones in George Griepp s PRG 420 class.

  NumberFormat nf = NumberFormat.getCurrencyInstance();
  int Monthly = 0;
  int monthcount = 0;
  String Output = "";

  int i = 0; // For first loop
  double loanamount = Double.parseDouble( tempTextField3.getText() );        //all loan amounts  are the same  
  double rate = Double.parseDouble( tempTextField1.getText() );     //Array for the rate
  double time = Double.parseDouble( tempTextField2.getText() );         //Array for the time
  double totalnumpayments = 0;         //Set for 
  double monthlypayment = 0; //Set for math calculation in first loop
  double interestPayment = 0;            //Set for math calculation in first loop
  double totaltime = 0; //Set for second loop to know how long to loop
  double loan = 0; //Set for second loop
  double interestPayment2 = 0; //Set for second loop
  double principlePayment = 0;  //Set for second loop


  for ( i = 0; i < time; i++ ) {//First loop This loops through the arrays and gives the first message listed below three times
    monthlypayment = ( loanamount * ( ( rate / 12 ) / ( 1 - Math.pow( ( 1 + ( rate / 12 ) ), -( time * 12 ) ) ) ) );
    interestPayment = loanamount * ( rate * 100 / 1200 );
    totaltime = ( time * 12 );


    jTextArea1.setText( "" );
    jTextArea1.setText( "This loan has an interest rate of " + ( rate * 100 ) + "%" + " and a starting loan amount of " + nf.format( loanamount ) );
    jTextArea1.setText( "Payment Number		" + "Towards Principle		" + "Towards Interest	" + "Remaining on loan" );
    jTextArea1.setText( "" ); // Part of the first loop this will appear three times with the math listed above


    System.out.println( totaltime );
    Monthly++;

    Output += ( ( monthcount++ ) + "			" + nf.format( principlePayment ) + "			" + nf.format( interestPayment2 ) + "			" + nf.format( loan - principlePayment ) + "
" );


    loan = -principlePayment;// Changes the numbers as the loop goes
    interestPayment2 = loan * ( rate * 100 / 1200 );// Changes the numbers as the loop goes
    principlePayment = monthlypayment - interestPayment2;// Changes the numbers as the loop goes

  }
  jTextArea1.setText( Output );
}

Answer 1

有几个问题,可能不是(我不熟悉loans 。

You calculated totaltime in your for-loop, without making use of the i variable. Hence it will always result in the same result, and can be calculated outside the loop
By calling setText on the jTextArea1 inside the loop, where your last call is with the empty String, you might as well clear it before entering the for-loop, as in the end the jTextArea1 will just be empty. Or just remove the code since after the for loop you set the text to Output
The loan = -principlePayment is a weird statement. So if the principlePayment is a positive number, loan will be a negative number, and interestPayment2 as well
You would better use a StringBuilder to construct your Output variable

I think number 3 is the most important for your calculations.

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