如何解决连续计算器
我正在制作一个计算器，您可以在其中询问两个数字和一个运算。如果用户想继续，要求一个号码和一个操作。然后，使用最近的结果和新的输入值执行选定的操作。 我被困在存储上次操作的结果以将其用于另一个操作。这是我的代码
import java.util.Scanner;
public class practice {
static double add,sub,mul,div;
static double another;
public static void main(String[] args) {
char choose,cont;
Scanner u = new Scanner(system.in);
System.out.print("Enter number 1: ");
double one = Double.parseDouble(u.nextLine());
System.out.print("Enter number 2: ");
double two = Double.parseDouble(u.nextLine());
do {
System.out.print("\nSelect an operation\n[A]Addition\n[B]Subtraction\n[C]Multiplication\n[D]Division");
System.out.print("\n\nChoose: ");
choose = u.next().charat(0);
if ((choose == 'A') || (choose == 'a')) {
add = one + two;
add += another;
System.out.println("The sum is " + add);
} else if (choose == 'B' || choose == 'b') {
sub = one - two;
sub -= another;
System.out.println("The difference is " + sub);
} else if (choose == 'C' || choose == 'c') {
mul = one * two;
mul *= another;
System.out.println("The product is " + mul);
} else if (choose == 'D' || choose == 'd') {
div = one / two;
div /= another;
System.out.println("The quotient is " + div);
} else {
System.out.println("Invalid Selection");
}
System.out.print("Continue?[Y/N]: ");
cont = u.next().charat(0);
if (cont == 'Y') {
System.out.print("Enter another number: ");
another = u.nextDouble();
another = another;
} else {
System.out.println("End of Program");
}
} while (cont == 'Y');
}
}
解决方法
您可以将最后一个值的值置于循环之外。下面是一些伪代码来演示我的意思：
variableStore = 0
loop:
perform operations
when printing out results to the user,assign variableStore = result
Next time,variableStore would be the value of the previous result
您不需要所有这些变量。变量 one 总是 存储最新的结果。此外，由于您的类只包含一个方法，即 main，因此无需声明类成员变量。请参阅解释变量范围的 Java Language specification 的第 6.3 节。该链接适用于 Java 7，但对所有 Java 版本都有效。
这是我对 practice 类的重写。请注意，我将类名更改为 Practice，以与 Java naming conventions 保持一致。
import java.util.Scanner;
public class Practice {
public static void main(String[] args) {
char choose,cont = 'Y';
Scanner u = new Scanner(System.in);
System.out.print("Enter number 1: ");
double one = Double.parseDouble(u.nextLine());
double two = 0;
boolean invalidSelection = false;
do {
if (!invalidSelection) {
System.out.print("Enter another number: ");
two = Double.parseDouble(u.nextLine());
}
invalidSelection = false;
System.out.print(
"\nSelect an operation\n[A]Addition\n[B]Subtraction\n[C]Multiplication\n[D]Division");
System.out.print("\n\nChoose: ");
choose = u.nextLine().charAt(0);
if ((choose == 'A') || (choose == 'a')) {
one += two;
System.out.println("The sum is " + one);
}
else if (choose == 'B' || choose == 'b') {
one -= two;
System.out.println("The difference is " + one);
}
else if (choose == 'C' || choose == 'c') {
one *= two;
System.out.println("The product is " + one);
}
else if (choose == 'D' || choose == 'd') {
one /= two;
System.out.println("The quotient is " + one);
}
else {
System.out.println("Invalid Selection");
invalidSelection = true;
continue;
}
System.out.print("Continue?[Y/N]: ");
cont = u.nextLine().charAt(0);
} while (cont == 'Y' || cont == 'y');
System.out.println("End of Program");
}
}
请注意，在上面的代码中，我用对方法 next 的调用替换了对方法 java.util.Scanner（属于 nextLine 类）的调用。有关更多详细信息，请参阅此 SO 问题。
Scanner is skipping nextLine() after using next() or nextFoo()?
我建议您使用调试器运行代码以了解其工作原理。
这是示例运行的输出。
Enter number 1: 3
Enter another number: 2
Select an operation
[A]Addition
[B]Subtraction
[C]Multiplication
[D]Division
Choose: x
Invalid Selection
Select an operation
[A]Addition
[B]Subtraction
[C]Multiplication
[D]Division
Choose: c
The product is 6.0
Continue?[Y/N]: y
Enter another number: 4
Select an operation
[A]Addition
[B]Subtraction
[C]Multiplication
[D]Division
Choose: b
The difference is 2.0
Continue?[Y/N]: y
Enter another number: 0.5
Select an operation
[A]Addition
[B]Subtraction
[C]Multiplication
[D]Division
Choose: d
The quotient is 4.0
Continue?[Y/N]: n
End of Program
试试这个代码（它对我有用）：
import java.util.Scanner;
public class practice {
static double prevAns = 0;
static double another;
static double one;
static double add,sub,mul,div;
static boolean contin = false;
public static void main (String []args){
while(true){
char choose,cont;
Scanner u=new Scanner(System.in);
if (!contin){
System.out.print("Enter number 1: ");
one= Double.parseDouble(u.nextLine());
} else {
one = prevAns;
}
System.out.print("Enter number 2: ");
double two= Double.parseDouble(u.nextLine());
System.out.print("\nSelect an operation\n[A]Addition\n[B]Subtraction\n[C]Multiplication\n[D]Division");
System.out.print("\n\nChoose: ");
choose=u.next().charAt(0);
if((choose=='A')||(choose=='a')){
add = one+two;
prevAns = add;
System.out.println("The sum is "+add);}
else if (choose=='B'||choose=='b') {
sub=one-two;
prevAns = sub;
System.out.println("The difference is "+sub);
}else if (choose=='C'||choose=='c'){
mul=one*two;
prevAns = mul;
System.out.println("The product is "+mul);
}else if(choose=='D'||choose=='d'){
div=one/two;
prevAns = div;
System.out.println("The quotient is "+ div);}
else{
System.out.println("Invalid Selection");
}
System.out.print("Continue?[Y/N]: ");
cont=u.next().charAt(0);
if(cont=='Y'){
contin = true;
} else{
System.out.println("End of Program");
}
}
}
}
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