使用 Java Scanner 打印整行字符串

Question

How do I get the following to print the string input? First I insert int and then insert a double and then insert string but the code does not return the whole string.

import java.util.Scanner;

public class TestScanner {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        int i = scan.nextInt();
        double d = scan.nextDouble();
        String s = scan.next();

        System.out.println("String: " + s);
        System.out.println("Double: " + d);
        System.out.println("Int: " + i);
    }
}

Here is a test result. As you can see from below it prints the int and double but not the string.

3
2.5
Hello World

String: Hello
Double: 2.5
Int: 3

Answer 1

It's because the scan.nextDouble() method does not consume the last newline character of your input, and thus that newline is consumed in the next call to scan.nextLine().

For this a blank scan.nextLine() call after scan.nextDouble() to consume rest of that line including newline.

This is a sample code which might help you understand the workaround possible :

public class newLineIssue {
    public static void main(String args[]) throws InterruptedException {
        Scanner scan = new Scanner(System.in);

        int i = scan.nextInt();
        double d = scan.nextDouble();
        scan.nextLine();
        String s = scan.nextLine();

        System.out.println("String: " + s);
        System.out.println("Double: " + d);
        System.out.println("Int: " + i);
        }
    }

I got the output as :

1
22.5
dsfgdsg
String: dsfgdsg
Double: 22.5
Int: 1

Answer 2

This is sample code to help you to print the entire line of String..

package com.practice;

import java.util.Scanner;

public class Practice {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
       
        int i = scan.nextInt();       // Read the Integer data type

         double d = scan.nextDouble();      // Read the Double data type
         
         scan.nextLine();          // Read the entire line of String
         String s = scan.nextLine();
                 
        System.out.println("String: " + s);
        System.out.println("Double: " + d);
        System.out.println("Int: " + i);
    }
}

Input

45
56.24
Hi i am java developer!

Output

String: Hi i am java developer!
Double: 56.24
Int: 45