的Java测试文件返回NULL

Question

我想用一个测试文件中读取几个对象，但我从第二步空步骤4

对于名字，如果我输入史蒂芬，我想获得ste123背部（123应该是一个随机数）

下面是代码：

public class Lab14Tester 
{ 

    public static void main(String[] args) 
    { 
     Introduction step1 = new Introduction(); 
     System.out.println(step1.giveline1()); 
     System.out.println(step1.giveline2()); 
     System.out.println(step1.giveline3()); 
     System.out.println(step1.giveline2()); 
     System.out.println(step1.giveline1()); 

     Scanner in= new Scanner(System.in); 
     System.out.print("\nName: "); 
     String inputname = in.nextLine(); 
     Username step2 = new Username(); 
     String givename = step2.givename(); 
     System.out.println("Your username is " + givename); 

     System.out.print("\nGive me a number: "); 
     int inputnumber =in.nextInt(); 
     OddEven step3 = new OddEven(); 
     System.out.println(step3.givenumbertype()); 

     System.out.print("\nGive me a number grade: "); 
     double grade = in.nextDouble(); 
     NumberToLetter step4 = new NumberToLetter(); 
     System.out.printf("\n%.1f", grade); 
     System.out.print(" is equal to a " + step4.giveletter()); 
    } 
} 


public class Username 
{ 

    private String subname; 
    private int randomnumber; 
    private String outputname; 

    public void getname(String inputname) 
    { 
     subname = inputname.substring(0,3); 
     randomnumber = (int)(Math.random()*1000); 
     outputname = subname + randomnumber; 
    } 

    public String givename() 
    { 
     return outputname; 
    } 
} 

Answer 1

你可能会遇到麻烦，因为你用串联整数的字符串。

试试这个：

public void getname(String inputname) 
{ 
    subname = inputname.substring(0,3); 
    randomnumber = (int)(Math.random()*1000); 

    String randomnumberAsString = String.valueOf(randomnumber); 

    outputname = subname + randomnumberAsString; 
}