missing return

Question about the task

ConsoleReader class

Java Syntax, Level 6, Lesson 8

Under discussion

missing return statement not really sure if there's something wrong

Make the ConsoleReader class, which will have 4 static methods:
String readString() - reads a string from the keyboard
int readInt() - reads a number from the keyboard
double readDouble() - reads a fractional number from the keyboard
boolean readBoolean() - reads the string "true" or "false" from the keyboard and returns the corresponding boolean value (true or false)

Please note: In each method, create a variable to read data from the console (BufferedReader or Scanner).

Requirements:

The readString method must read and return a String.
The readInt method must read and return an int.
The readDouble method must read and return a double.
The readBoolean method must read and return a boolean value.

package com.codegym.task.task06.task0610; import java.io.BufferedReader; import java.io.InputStreamReader; /* ConsoleReader class */ public class ConsoleReader { public static String readString() throws Exception { BufferedReader dog = new BufferedReader(new InputStreamReader(System.in)); return dog.readLine(); //write your code here } public static int readInt() throws Exception { //write your code here BufferedReader dog = new BufferedReader(new InputStreamReader(System.in)); return Integer.parseInt(dog.readLine()); } public static double readDouble() throws Exception { //write your code here BufferedReader dog = new BufferedReader(new InputStreamReader(System.in)); return Double.parseDouble(dog.readLine()); } public static boolean readBoolean() throws Exception { //write your code here BufferedReader dog = new BufferedReader(new InputStreamReader(System.in)); String s = dog.readLine(); Boolean readBoolean = false; if(s.equals("true")){ return !readBoolean; } else if(s.equals("false")){ return readBoolean; } } public static void main(String[] args) { } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

24 October 2020, 14:30

The problem is lines 37-42. When putting things behind logic gates such as if statements, there is no guarantee that one of statements will be reached. It doesn't matter to the computer if it logically can be reached or not. Some examples of things that this effects are return statements and variable initialization. In your case if the user enters anything other than "true" or "false", a return statement will not be reached. An examples:

int var;
if("yes".equals("yes")) var = 35;
System.out.println(var);

This is illegal code because the initialization of "var" is behind a logic gate. Even though the boolean expression of "yes equals yes" will always be true, the computer doesn't care. The illegal line would be the third one in which the potentially uninitialized variable is used. If you remove that line the code will run. To fix this you can either initialize the variable on line 1, or add an else clause that initializes the variable in case the if statement is false:

// option #1
int var = 0; // initialize var to a default value
if("yes".equals("yes")) var = 35;
System.out.println(var); // now this line is legal

// option #2
int var;
if("yes".equals("yes")) var = 35;
else var = 25; // add this so ALL code paths result in a proper initialization or return statement
System.out.println(var); // now this line is legal

Guanting Liu

Level 0 , Springfield, United States

Expert

24 October 2020, 14:46

I delete the boolean value instead I use .equals() to test if " true" return true; "false" return false;why it is still saying returning missing?Bro,your point is pretty good I totally agree with your idea but I think something else might happen also.

Guadalupe Gagnon

Level 37 , Tampa, United States

24 October 2020, 23:08

are the return statements still behind logic gates?