I have to write a java program that asks users to enter data values, until they enter a blank line. But I have a problem that I have to enter twice to stop asking input and i only can solve this problem when adding a System.out.prinln() line. How can i fix it, pleas help me.

This is my code:

System.out.println("Enter components: ");
    Set<String> comps = new Set<>();
    while (true) {
        String comp = scan.nextLine();
        if (comp.equals("")) {
            break;
        } else {
            comps.insert(comp);
            scan.nextLine();     // also if i remove this line, the input only asked twice
            System.out.println();     // can solve the prob when add this
        }
    }

When i run my program, it will asks for the input like this:

enter image description here

CodePudding user response：

You only need one Scanner nextLine call.

System.out.println("Enter components: ");
Set<String> comps = new Set<>();
while (true) {
    String comp = scan.nextLine();
    if (comp.equals("")) {
        break;
    } else {
        comps.insert(comp);
    }
}

CodePudding user response：

Here you need to feed only one empty line and the loop will break.

String comp = scan.nextLine();

while (!comp.equals("")) {
    comps.add(comp);
    comp = scan.nextLine();
}