Java – exception处理 – 如何重新输入无效输入

exception处理仅接受双输入。 因此，当用户输入“k”时，它会显示“错误！请输入一个数字！”。 但是，它不是允许用户重新输入输入，而是跳转到下一个输入“平均脉冲”。如何使其工作以使其保持在同一条线上并允许重新输入值？

//主要课程

public class Main { //Master class public static void main( String args[] ) //Standard header for main method { kbentry input = new kbentry(); //Creates object of kbentry class System.out.print("\nPlease enter a number for Total Impulse: " ); //Print message to enter 1. input double totalImpulse = input.totalImpulse1(); //Holds the variable entered System.out.println("You have entered : " + totalImpulse); //Shows the variable entered System.out.print("\nPlease enter a number for Average Impulse: " ); //Print message to enter 2. input double averageImpulse = input.averageImpulse2(); //Holds the variable entered System.out.println("You have entered : " + averageImpulse); //Shows the variable entered } } 

// kbentry类

  import java.io.BufferedReader; import java.io.InputStreamReader; import java.io.IOException; public class kbentry{ //Class name double totalImpulse1(){ //Method for 1. input BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); //Creates BufferedReader object for System.in //Total Impulse entry String strTotalImpulse = null; // These must be initialised double intTotalImpulse = 0; //Setting it double try { strTotalImpulse = in.readLine(); //Reads string value from the keyboard } catch (IOException ioe) { // ignore exception } try { intTotalImpulse = Double.parseDouble(strTotalImpulse); // convert it to double } catch (NumberFormatException nfe) { System.out.println("Error! Please enter a number!" + nfe.toString()); //Error message if its not a double } return intTotalImpulse; //return value } double averageImpulse2(){ //Method for 2. input BufferedReader in = new BufferedReader(new InputStreamReader(System.in));//Creates BufferedReader object for System.in // String for AverageImpulse String strAverageImpulse = null; // These must be initialised double intAverageImpulse = 0; //Setting it double try { strAverageImpulse = in.readLine(); //Reads string value from the keyboard } catch (IOException ioe) { // ignore exception } // convert it to integer try { intAverageImpulse = Double.parseDouble(strAverageImpulse); // convert it to double } catch (NumberFormatException nfe) { System.out.println("Error! Please enter a number!" + nfe.toString()); //Error message if its not a double } return intAverageImpulse; //return value } } 

Answer 1

如果用户输入的不是double，那么你将获得NumberFormatException，因为你必须再次调用该方法

 catch (NumberFormatException nfe) { System.out.println("Error! Please enter a number!" + nfe.toString()); //Error message if its not a double //again ask for input System.out.print("\nPlease enter a number for Total Impulse: "); return totalImpulse1(); }