Java Scanner class reading strings
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13-09-2019 - |
Question
I got the following code:
int nnames;
String names[];
System.out.print("How many names are you going to save: ");
Scanner in = new Scanner(System.in);
nnames = in.nextInt();
names = new String[nnames];
for (int i = 0; i < names.length; i++){
System.out.print("Type a name: ");
names[i] = in.nextLine();
}
And the output for that code is the following:
How many names are you going to save:3
Type a name: Type a name: John Doe
Type a name: John Lennon
Notice how it skipped the first name entry?? It skipped it and went straight for the second name entry. I have tried looking what causes this but I don't seem to be able to nail it. I hope someone can help me. Thanks
Solution
The reason for the error is that the nextInt only pulls the integer, not the newline. If you add a in.nextLine() before your for loop, it will eat the empty new line and allow you to enter 3 names.
int nnames;
String names[];
System.out.print("How many names are you going to save: ");
Scanner in = new Scanner(System.in);
nnames = in.nextInt();
names = new String[nnames];
in.nextLine();
for (int i = 0; i < names.length; i++){
System.out.print("Type a name: ");
names[i] = in.nextLine();
}
or just read the line and parse the value as an Integer.
int nnames;
String names[];
System.out.print("How many names are you going to save: ");
Scanner in = new Scanner(System.in);
nnames = Integer.parseInt(in.nextLine().trim());
names = new String[nnames];
for (int i = 0; i < names.length; i++){
System.out.print("Type a name: ");
names[i] = in.nextLine();
}
OTHER TIPS
use sc.nextLine(); two time so that we can read the last line of string
sc.nextLine() sc.nextLine()
It's because the in.nextInt() doesn't change line. So you first "enter" (after you press 3 ) cause the endOfLine read by your in.nextLine() in your loop.
Here a small change that you can do:
int nnames;
String names[];
System.out.print("How many names are you going to save: ");
Scanner in = new Scanner(System.in);
nnames = Integer.parseInt(in.nextLine());
names = new String[nnames];
for (int i = 0; i < names.length; i++){
System.out.print("Type a name: ");
names[i] = in.nextLine();
}
This because in.nextInt() only receive a int number, doesn't receive a new line. So you input 3 and press "Enter", the end of line is read by in.nextline().
Here is my code:
int nnames;
String names[];
System.out.print("How many names are you going to save: ");
Scanner in = new Scanner(System.in);
nnames = in.nextInt();
in.nextLine();
names = new String[nnames];
for (int i = 0; i < names.length; i++){
System.out.print("Type a name: ");
names[i] = in.nextLine();
}
You could have simply replaced
names[i] = in.nextLine();
with names[i] = in.next();
Using next() will only return what comes before a space. nextLine() automatically moves the scanner down after returning the current line.