Java 扫描仪使用nextInt()和循环不断跳过输入whist
我使用while循环来确保输入到scanner对象的值是一个整数,如下所示:Java 扫描仪使用nextInt()和循环不断跳过输入whist,java,loops,java.util.scanner,next,Java,Loops,Java.util.scanner,Next,我使用while循环来确保输入到scanner对象的值是一个整数,如下所示: while (!capacityCheck) { try { System.out.println("Capacity"); capacity = scan.nextInt(); capacityCheck = true; } catch (InputMismatchException e) {
while (!capacityCheck) {
try {
System.out.println("Capacity");
capacity = scan.nextInt();
capacityCheck = true;
} catch (InputMismatchException e) {
System.out.println("Capacity must be an integer");
}
}
但是,如果用户没有输入整数,当它应该返回并接受另一个输入时,它只是重复打印容量,然后在catch中输出,而不要求更多的输入。如何停止此操作?尝试将此操作放在循环的末尾-
scan.nextLine();
或者最好把它放在挡块里
while (!capacityCheck) {
try {
System.out.println("Capacity");
capacity = scan.nextInt();
capacityCheck = true;
} catch (InputMismatchException e) {
System.out.println("Capacity must be an integer");
scan.nextLine();
}
}
将这段代码放在catch块中,以使用非整数字符和保留在缓冲区中的新行字符,因此,在输入错误的情况下,无限打印catch sysout
当然,还有其他更干净的方法来实现您想要的,但我想这需要对代码进行一些重构。使用以下方法:
while (!capacityCheck) {
System.out.println("Capacity");
String input = scan.nextLine();
try {
capacity = Integer.parseInt(input );
capacityCheck = true;
} catch (NumberFormatException e) {
System.out.println("Capacity must be an integer");
}
}
试试这个:
while (!capacityCheck) {
try {
System.out.println("Capacity");
capacity = scan.nextInt();
capacityCheck = true;
} catch (InputMismatchException e) {
System.out.println("Capacity must be an integer");
scan.nextLine();
}
}
我认为不需要try/catch或capacityCheck,因为我们可以访问方法hasNextInt,该方法检查下一个标记是否为int。例如,这应该满足您的要求:
while (!scan.hasNextInt()) { //as long as the next is not a int - say you need to input an int and move forward to the next token.
System.out.println("Capacity must be an integer");
scan.next();
}
capacity = scan.nextInt(); //scan.hasNextInt() returned true in the while-clause so this will be valid.
它需要使用换行符。为什么要放scan.nextLine;?scan.nextInt将只扫描下一个整数,但当它不是正确的输入时,输入的无效字符将停留在那里,而不会被消耗,从而使while进入无限循环。更新我的答案!:
while (!scan.hasNextInt()) { //as long as the next is not a int - say you need to input an int and move forward to the next token.
System.out.println("Capacity must be an integer");
scan.next();
}
capacity = scan.nextInt(); //scan.hasNextInt() returned true in the while-clause so this will be valid.