打印輸出語句的格式化問題，雙打java

Question

我是一個新手試圖讓我的打印輸出語句來格式化小數點位置..我知道％.2f的作品，但無論什麼原因，當我嘗試應用％ .2炸彈......不知道該怎麼辦..有什麼建議嗎？提前致謝！

credits = int 

raise = double 

System.out.printf("An undergraduate resident student taking " + credits + " currently pays $" + "%,.2f",credtotal); 

System.out.println("\n"); 

System.out.printf("with a increase in tuition of " + (trying to format here) raise + ", per credit will become " + raisecredund + ", and an undergraduate resident taking " + credits + " credits" + " will pay $" +"%,.2f",(credits*(raise*245.73))+ credtotal);; 

Answer 1

final String str1 = String.format("An undergraduate resident student taking %d currently pays $%.2f",credits, credtotal); 

編輯：您正在使用printf我沒有注意到。你接近：

System.out.printf("An undergraduate resident student taking %d currently pays $%.2f", credits,credtotal); 

使用你的第一個例子中的字符串，您提供的格式化字符內聯，然後爲每個佔位符的參數。假設credtotal是雙和知道credits是int，上面將產生（用分配各自的值）

An undergraduate resident student taking 1 currently pays $2.00 

參見creating formatted strings section。

Answer 2

您似乎在使用"%,.2f"時使用逗號，我認爲這不是合法的。 %.2f將打印數字到2位小數。

如果你想永遠包含一個逗號3個地方像錢你應該使用一個DecimalFormat
DecimalFormat formatter = new DecimalFormat("#,###.00");