当我调用方法 f() 时，控制台中什么也没有出现。 为什么？

Question

package Evaluare1;

import java.util.*;

public class e15 {

    public static void main(String[]args){

        Scanner s = new Scanner(System.in);

        int a = s.nextInt();

        f(a);
        //i don't have errors when i run it
        }

    //this method won't return the value when i call it

    public static int f(int x){
        if(x%2 <= 0){
            return x/2;
        }else   
            return x * 3 + 1;
    }
}

How can I fix this?

Answer 1

If what you want to do is print the result of f() than you cannot simply invoke the function as all that will do is return the result, which you are ignoring. Instead try something like this:

import java.util.*;
public class e15 {

    public static void main(String[]args){

        Scanner s = new Scanner(System.in);

        int a = s.nextInt();

        System.out.println(f(a));
        //i don't have errors when i run it
    }

    //this method won't return the value when i call it

    public static int f(int x){
        if(x%2 <= 0){
            return x/2;
        }
        else
            return x * 3 + 1;
    }
}

Note the System.out.println(f(a)); . This will print your result to standard out, typically your shell.

Answer 2

添加 System.out.println() 以在控制台上打印。

Answer 3

If you are trying to learn java try to use different methods present in the PrintStream.class

For example,

public class e15 {
  public static void main(String[]args){

        Scanner s = new Scanner(System.in);

        int a = s.nextInt();

        System.out.print(f(a));
        //i don't have errors when i run it
        }

    //this method won't return the value when i call it

    public static int f(int x){
        if(x%2 <= 0){
            return x/2;
        }else   
            return x * 3 + 1;
    }}

In this I have used the print function present in the PrintStream class, it prints the particular integer (overloaded method), you could also use printf, where you want to insert the value at the exact position of the string without concatenation, use %s for string %d for Numbers like that.

The advantages of println is that it prints in the new line.

Play around it would be fun.