如何检查变量是否等于包含?我想这样做,如果某人放在一个无效的操作员,它会说再试一次。
String operator = "+, -, *,/, %";
double num1, num2, sum=0;
System.out.println("First number: ");
num1 = input.nextDouble();
System.out.println("Second number: ");
num2 = input.nextDouble();
if (operator.contains("+")){
sum = num1 + num2;
} else if (operator != operator.contains("+,-,*,/,%"){
的System.out.println("错误&#34); }
答案 0 :(得分:1)
如果要根据用户条目检查应使用哪个运算符,可以使用switch
语句,如下所示
String operator = "";
while (operator.isEmpty()) {
System.out.println("Enter Operator: ");
operator = input.next();
switch (operator) {
case "+" : result = num1 + num2; break;
case "-" : result = num1 - num2; break;
case "*" : result = num1 * num2; break;
case "/" : result = num1 / num2; break;
default : System.out.println("Invalid operator: " + operator);
operator = "";
}
System.out.println("Result is " + result);
}
如果您只想检查运算符是否有效,可以使用List
contains()方法:
String[] operators = { "+", "-", "*", "/" , "%" };
List<String> ops = Arrays.asList(operators);
:
System.out.println("Enter Operator: ");
String operator = input.next();
if (ops.contains(operator)) {
// do some calculation here
}