I am writing a java program for user input of a string representing an 8-digit binary number. If the input is valid the program should count the 1's and if its not valid it should prompt the user for a valid entry. I've found renditions of this code online but still can't find my error. I am using Eclipse IDE 2021-12 and Java 17.0.1.
import java.util.Scanner;
public class Chapter6PA1 {
public static void main(String[]args){
//initialize variables and input
Scanner sc = new Scanner(System.in);
String word = "";//user input word
int count=0;//the number of 1s in the word
boolean isValid = false;//initialize boolean to be false until conditions are met for valid binary number
do {
for(int i=0; i <word.length()-1; i ) {
System.out.println("Please enter a valid binary number: ");//prompts user input
word = sc.nextLine();//determines input is equal to string word
if(word.length()==7){
if(word.charAt(i)=='1'||word.charAt(i)=='0'){
if(word.charAt(i)=='1');
isValid = true;//when the above conditions are met then we have a valid binary number
count ;//count will increment each time a character is equal to 1
System.out.println("The binary number you entered contains " count " ones.");
}
}
else {
System.out.println("Invalid binary number.Please enter an 8-digit word containing only 1s and 0s.");
break;
}
}
}while(isValid);
}
}
this is where im at now, i initialize the String declaration inside the do loop and now the program output is incorrect. here is code.
import java.util.Scanner;
public class Chapter6PA1 {
public static void main(String[]args){
//initialize variables and input
Scanner sc = new Scanner(System.in);
int count=0;//the number of 1s in the word
boolean isValid = false;//initialize boolean to be false until conditions are met for valid binary number
do {
System.out.println("Please enter a valid binary number: ");//prompts user input
String word = sc.nextLine();//determines input is equal to string word//user input word
for(int i=0; i <word.length()-1; i ) {
if(word.length()==8){
if(word.charAt(i)=='1'||word.charAt(i)=='0'){
if(word.charAt(i)=='1');
isValid = true;//when the above conditions are met then we have a valid binary number
count ;//count will increment each time a character is equal to 1
System.out.println("The binary number you entered contains " count " ones.");
}
}
else {
System.out.println("Invalid binary number.Please enter an 8-digit word containing only 1s and 0s.");
break;
}
}
}while(!isValid);
}
}
and here is output:
>Please enter a valid binary number:
>0101
>Invalid binary number.Please enter an 8-digit word containing only 1s and 0s.
>Please enter a valid binary number:
>01010101
>The binary number you entered contains 1 ones.
>The binary number you entered contains 2 ones.
>The binary number you entered contains 3 ones.
>The binary number you entered contains 4 ones.
>The binary number you entered contains 5 ones.
>The binary number you entered contains 6 ones.
>The binary number you entered contains 7 ones.
CodePudding user response：
Because the String word is empty and when it goes to the for loop it checks where i which is 0, is less than the length-1 of the String word which is 0 as well hence it does not go inside the for loop.
So replace the below line,
String word = "";//user input word
With these lines in the for loop above the loop
System.out.println("Please enter a valid binary number: ");//prompts user input
String word = sc.nextLine();//determines input is equal to string word
CodePudding user response：
As already mentioned by @ bdavidson024 the word is initially empty so the loop breaks without executing. Also the condition inside the while loop should be !isValid
Try the following code:
public static void main(String[]args){
//initialize variables and input
Scanner sc = new Scanner(System.in);
String word="";//user input word
int count=0;//the number of 1s in the word
boolean isValid = false;//initialize boolean to be false until conditions are met for valid binary number
do {
System.out.println("Please enter a valid binary number: ");//prompts user input
word = sc.nextLine();//determines input is equal to string word
if(word.length()==8){
isValid = true;
for(int i=0; i <word.length(); i ) {
if(word.charAt(i)=='1'||word.charAt(i)=='0'){
if(word.charAt(i)=='1'){
count ;//count will increment each time a character is equal to 1
}
}
else break;
}
System.out.println("The binary number you entered contains " count " ones.");
}
else {
System.out.println("Invalid binary number.Please enter an 8-digit word containing only 1s and 0s.");
isValid = false;
}
} while(!isValid);
}
CodePudding user response：
thanks guys here is the correct code @Naman just change the loop condition!
public static void main(String[]args){
//initialize variables and input
Scanner sc = new Scanner(System.in);
int count=0;//the number of 1s in the word
boolean isValid = false;//initialize boolean to be false until conditions are met for valid binary number
do {
System.out.println("Please enter a valid binary number: ");//prompts user input
String word = sc.nextLine();//determines input is equal to string word//user input word
if(word.length()==8){
isValid = true;//when the above conditions are met then we have a valid binary number
for(int i=0; i <word.length()-1; i ) {
if(word.charAt(i)=='1'||word.charAt(i)=='0'){
if(word.charAt(i)=='1') {
count ;//count will increment each time a character is equal to 1
}
}
else break;
}
System.out.println("The binary number you entered contains " count " ones.");
}
else {
System.out.println("Invalid binary number.Please enter an 8-digit word containing only 1s and 0s.");
isValid=false;
}
}while(!isValid);
}
}