java do while循环在满足条件后保持循环
我是一名新的java程序员，我正在编写一个程序，为3台打印机设置3个型号。如果用户输入了错误的值，我希望它继续向用户询问型号。我让它工作，但只有当用户的第一个值是3台打印机之一的数字时。如果第一个值不是一个可能的值，而第二个输入是，它仍然会重复循环java do while循环在满足条件后保持循环,java,loops,do-while,Java,Loops,Do While,我是一名新的java程序员，我正在编写一个程序，为3台打印机设置3个型号。如果用户输入了错误的值，我希望它继续向用户询问型号。我让它工作，但只有当用户的第一个值是3台打印机之一的数字时。如果第一个值不是一个可能的值，而第二个输入是，它仍然会重复循环 package printing; import java.util.Scanner; public class newClass { public static void main(String[] args) {
package printing;
import java.util.Scanner;
public class newClass {
public static void main(String[] args) {
int count = 0;
String machine1 = "546";
String machine2 = "892";
String machine3 = "127";
Scanner s = new Scanner(System.in);
System.out.print("Model Number:");
String modelNumber = s.nextLine();
// increment count if first input value is wrong
if (!s.equals(machine1) || !s.equals(machine2) || !s.equals(machine3))
count++;
// if user inputs right value
while (true) {
if (modelNumber.equals(machine1)) {
System.out.println("Machine 1 is online");
break;
}
if (modelNumber.equals(machine2)) {
System.out.println("Machine 2 is online");
break;
}
if (modelNumber.equals(machine3)) {
System.out.println("Machine 3 is online");
break;
}
// keep looping if user does not input values for machine1, machine2 or machine3
do {
System.out.println("Try again");
System.out.print("Model Number:");
String modelNumberFalse = s.nextLine();
/* each time user gets value wrong the count variable goes up by 1 and
the loop breaks when count reaches 3 */
count++;
if (count == 3)
break;
} while (!s.equals(machine1) || (!s.equals(machine2)) || (!s.equals(machine3)) && (count < 2));
}
}
}
包装印刷；
导入java.util.Scanner；
公共类新类{
公共静态void main（字符串[]args）{
整数计数=0；
字符串机1=“546”；
字符串机2=“892”；
字符串机3=“127”；
扫描仪s=新的扫描仪（System.in）；
系统输出打印（“型号：”）；
字符串modelNumber=s.nextLine（）；
//第一个输入值错误时的增量计数
如果（！s.equals（machine1）| |！s.equals（machine2）| |！s.equals（machine3））
计数++；
//如果用户输入正确的值
while（true）{
if（型号等于（机器1））{
System.out.println（“机器1在线”）；
打破
}
if（modelNumber.equals（machine2））{
System.out.println（“机器2在线”）；
打破
}
if（型号等于（机器3））{
System.out.println（“机器3在线”）；
打破
}
//如果用户未输入machine1、machine2或machine3的值，请保持循环
做{
System.out.println（“重试”）；
系统输出打印（“型号：”）；
字符串modelNumberFalse=s.nextLine（）；
/*每次用户获得错误的值时，count变量都会增加1和
当计数达到3时，循环中断*/
计数++；
如果（计数=3）
打破
}而（！s.equals（machine1）| |（！s.equals（machine2））| |（！s.equals（machine3））&&&（count<2））；
}
}
}
此外，每次用户输入错误的值时，我希望count变量递增，直到达到3，do while循环中断，但在我输入错误的值超过3次后，它会不断询问型号 有几个问题。这一行是错误的：
while(!s.equals(machine1) || (!s.equals(machine2)) || (!s.equals(machine3)) && (count < 2));
package printing;
import java.util.Scanner;
public class newClass {
public static void main(String[] args) {
int count = 0;
String machine1 = "546";
String machine2 = "892";
String machine3 = "127";
Scanner s = new Scanner(System.in);
System.out.print("Model Number:");
String modelNumber = s.nextLine();
// increment count if first input value is wrong
if (!s.equals(machine1) || !s.equals(machine2) || !s.equals(machine3))
count++;
// if user inputs right value
while (true) {
if (modelNumber.equals(machine1)) {
System.out.println("Machine 1 is online");
break;
}
if (modelNumber.equals(machine2)) {
System.out.println("Machine 2 is online");
break;
}
if (modelNumber.equals(machine3)) {
System.out.println("Machine 3 is online");
break;
}
// keep looping if user does not input values for machine1, machine2 or machine3
do {
System.out.println("Try again");
System.out.print("Model Number:");
String modelNumberFalse = s.nextLine();
/* each time user gets value wrong the count variable goes up by 1 and
the loop breaks when count reaches 3 */
count++;
if (count == 3)
break;
} while (!s.equals(machine1) || (!s.equals(machine2)) || (!s.equals(machine3)) && (count < 2));
}
}
}
while(!modelNumber.equals(machine1)
&& (!modelNumber.equals(machine2))
&& (!modelNumber.equals(machine3)));
while(!(modelNumber.equals(machine1)
|| modelNumber.equals(machine2)
|| modelNumber.equals(machine3)))
此外，如果您将“return”替换为“break”；并对do while条件进行更改，则它会起作用。所以还有别的事情发生。在内部do while中调用break会导致控件返回到外部while循环的顶部。添加一个在中断之前设置并在外部while循环中测试的布尔标志将是解决此问题的一种方法。或者直接使用return。有几个问题。这一行是错误的：
while(!s.equals(machine1) || (!s.equals(machine2)) || (!s.equals(machine3)) && (count < 2));
import java.util.Scanner;
public class newClass
{
public static void main(String[] args)
{
int count = 0;
String machine1 = "546";
String machine2 = "892";
String machine3 = "127";
Scanner s = new Scanner(System.in);
while (true)
{
System.out.print("Model Number:");
String modelNumber = s.nextLine();
// increment count if first input value is wrong
if ((!modelNumber.equals(machine1)) || (!modelNumber.equals(machine2)) || (!modelNumber.equals(machine3)))
count++;
if (count == 3)
{
System.out.println("You have utilized your maximum number of try's");
break;
}
if (modelNumber.equals(machine1))
{
System.out.println("Machine 1 is online");
break;
}
if (modelNumber.equals(machine2))
{
System.out.println("Machine 2 is online");
break;
}
if (modelNumber.equals(machine3))
{
System.out.println("Machine 3 is online");
break;
}
System.out.println("Try again");
}
}
}
package printing;
import java.util.Scanner;
public class newClass {
public static void main(String[] args) {
int count = 0;
String machine1 = "546";
String machine2 = "892";
String machine3 = "127";
Scanner s = new Scanner(System.in);
System.out.print("Model Number:");
String modelNumber = s.nextLine();
// increment count if first input value is wrong
if (!s.equals(machine1) || !s.equals(machine2) || !s.equals(machine3))
count++;
// if user inputs right value
while (true) {
if (modelNumber.equals(machine1)) {
System.out.println("Machine 1 is online");
break;
}
if (modelNumber.equals(machine2)) {
System.out.println("Machine 2 is online");
break;
}
if (modelNumber.equals(machine3)) {
System.out.println("Machine 3 is online");
break;
}
// keep looping if user does not input values for machine1, machine2 or machine3
do {
System.out.println("Try again");
System.out.print("Model Number:");
String modelNumberFalse = s.nextLine();
/* each time user gets value wrong the count variable goes up by 1 and
the loop breaks when count reaches 3 */
count++;
if (count == 3)
break;
} while (!s.equals(machine1) || (!s.equals(machine2)) || (!s.equals(machine3)) && (count < 2));
}
}
}
while(!modelNumber.equals(machine1)
&& (!modelNumber.equals(machine2))
&& (!modelNumber.equals(machine3)));
while(!(modelNumber.equals(machine1)
|| modelNumber.equals(machine2)
|| modelNumber.equals(machine3)))
import java.util.Scanner;
public class newClass
{
public static void main(String[] args)
{
int count = 0;
String machine1 = "546";
String machine2 = "892";
String machine3 = "127";
Scanner s = new Scanner(System.in);
while (true)
{
System.out.print("Model Number:");
String modelNumber = s.nextLine();
// increment count if first input value is wrong
if ((!modelNumber.equals(machine1)) || (!modelNumber.equals(machine2)) || (!modelNumber.equals(machine3)))
count++;
if (count == 3)
{
System.out.println("You have utilized your maximum number of try's");
break;
}
if (modelNumber.equals(machine1))
{
System.out.println("Machine 1 is online");
break;
}
if (modelNumber.equals(machine2))
{
System.out.println("Machine 2 is online");
break;
}
if (modelNumber.equals(machine3))
{
System.out.println("Machine 3 is online");
break;
}
System.out.println("Try again");
}
}
}
- 第一：不使用或不需要时使用
- 第二：你在重复 这次考试没有什么好理由
import java.util.Scanner;
public class newClass {
public static void main(String[] args) {
int count = 0;
// for extra credit, try to make this an ArrayList
// so you can keep adding models as needed
// then you would adjust your tests to leverage the ArrayList
// search functions
String machine1 = "546";
String machine2 = "892";
String machine3 = "127";
Scanner s = new Scanner(System.in);
// when using a while loop, it is good practice to use a boolean
// as your logic expands, multiple tests in the loop may set the
// boolean to true or false
// it is cumbersom to have large blocks of code in your while check
boolean keepOnTrucking = true;
System.out.print("Enter Model Number:");
while (keepOnTrucking) {
String modelNumber = s.nextLine();
// when using multiple tests, it is good
// to give each test its own line and end the line
// with the logical operator that joins it to the next
// it makes it easier to read
// and easier to edit (add or remove tests)
// Logical operator note:
// Your test was: not A OR not B OR not C
// This would NEVER work, as A != B != C
// If a user entered machine2, the check would
// fail for !(machine1), OR !(machine2) OR !(machine3)
// because while (!s.equals(machine2)) would say false
// (!s.equals(machine1)) would say true, and the OR
// chain would stop and count it as an error.
// Instead you want:
// !(machine1) && !(machine2) && !(machine3)
// Thus to to error, it has to not any of the machines.
// If it is true for all three nots, then you have an error
if (!machine1.equals(modelNumber) &&
!machine2.equals(modelNumber) &&
!machine3.equals(modelNumber)) {
// you only increment on failure
count++;
// nice developers give meaningful feed back to users
if (count>=3) {
System.out.print("Out of guesses! Go Away!"); // even when it is mean
// since you are nested in one while loop,
// this will break you out
break;
} else {
System.out.print("Not a valid model number, please re-enter:");
}
} else {
// the found a machine, so exit the while loop
keepOnTrucking = false;
if (machine1.equals(modelNumber)) {
System.out.println("Machine 1 is online");
} else if (machine1.equals(modelNumber)) {
System.out.println("Machine 2 is online");
} else { // since this ins the only one left, you don't need an if clause
System.out.println("Machine 3 is online");
}
}
}
}
}
- 第一：不使用或不需要时使用
- 第二：你在重复 这次考试没有什么好理由
import java.util.Scanner;
public class newClass {
public static void main(String[] args) {
int count = 0;
// for extra credit, try to make this an ArrayList
// so you can keep adding models as needed
// then you would adjust your tests to leverage the ArrayList
// search functions
String machine1 = "546";
String machine2 = "892";
String machine3 = "127";
Scanner s = new Scanner(System.in);
// when using a while loop, it is good practice to use a boolean
// as your logic expands, multiple tests in the loop may set the
// boolean to true or false
// it is cumbersom to have large blocks of code in your while check
boolean keepOnTrucking = true;
System.out.print("Enter Model Number:");
while (keepOnTrucking) {
String modelNumber = s.nextLine();
// when using multiple tests, it is good
// to give each test its own line and end the line
// with the logical operator that joins it to the next
// it makes it easier to read
// and easier to edit (add or remove tests)
// Logical operator note:
// Your test was: not A OR not B OR not C
// This would NEVER work, as A != B != C
// If a user entered machine2, the check would
// fail for !(machine1), OR !(machine2) OR !(machine3)
// because while (!s.equals(machine2)) would say false
// (!s.equals(machine1)) would say true, and the OR
// chain would stop and count it as an error.
// Instead you want:
// !(machine1) && !(machine2) && !(machine3)
// Thus to to error, it has to not any of the machines.
// If it is true for all three nots, then you have an error
if (!machine1.equals(modelNumber) &&
!machine2.equals(modelNumber) &&
!machine3.equals(modelNumber)) {
// you only increment on failure
count++;
// nice developers give meaningful feed back to users
if (count>=3) {
System.out.print("Out of guesses! Go Away!"); // even when it is mean
// since you are nested in one while loop,
// this will break you out
break;
} else {
System.out.print("Not a valid model number, please re-enter:");
}
} else {
// the found a machine, so exit the while loop
keepOnTrucking = false;
if (machine1.equals(modelNumber)) {
System.out.println("Machine 1 is online");
} else if (machine1.equals(modelNumber)) {
System.out.println("Machine 2 is online");
} else { // since this ins the only one left, you don't need an if clause
System.out.println("Machine 3 is online");
}
}
}
}
}
如何在一个while循环中编写它？thankshow我能把它写在一个while循环中吗？谢天谢地或者更好的办法是，删除否定词并使用，或者按照de morgan lawsWell，您可以将您的固定代码减少为：“应该是：
while（true）；while（true&&（true）&（true）&（true））while（true）while（true）扫描仪字符串，而（true）