变量重置 import java.util.Scanner； 导入javax.swing.JOptionPane； 公共类硬件{ 公共静态void main（字符串[]args）{ 余额=100； 布尔增益=真； while（goAgain==true）{ checkGuess（getGuess（），getBet（balance））； goAgain=goAgain（）； } } 公共静态字符串getGuess（）{ 扫描仪输入=新扫描仪（系统输入）； 字符串猜测=null； 布尔值validInput=false； while（validInput==false）{ System.out.println（“猜测：（H/T）”）； 猜测=in.next（）； 如果（猜测等于（“H”）|猜测等于（“T”））{ validInput=true； }否则{ showMessageDialog（null，“无效输入：”+猜测）； } } 返回猜测； } 公共静态双getBet（双余额）{ 扫描仪输入=新扫描仪（系统输入）； 字符串输入=null； 双betParsed=0； 布尔值validInput=false； while（validInput==false）{ System.out.println（“打赌？您有：$”+余额）； betInput=in.next（）； 试一试{ betParsed=Double.parseDouble（betInput）； }捕获（数字格式）{ showMessageDialog（null，“无效输入：”+betInput）； } 如果（betParsed>balance | | betParsed

，问题在于

updateBal

方法

您已经声明了一个

余额

类变量，但是您声明了另一个

余额

变量作为该方法的本地变量。您成功地更新了本地

余额

，但没有更新类

余额

---

首先，调用本地副本；同时在作用域中有两个同名的变量是令人困惑的。然后，在方法末尾，确保将该值赋回类变量

balance

问题在于

updateBal

方法

您已经声明了一个

余额

类变量，但是您声明了另一个

余额

变量作为该方法的本地变量。您成功地更新了本地

余额

，但没有更新类

余额

---

首先，调用本地副本；同时在作用域中有两个同名的变量是令人困惑的。然后，在方法末尾，确保将该值赋回类变量

balance

问题在于

updateBal

方法

您已经声明了一个

余额

类变量，但是您声明了另一个

余额

变量作为该方法的本地变量。您成功地更新了本地

余额

，但没有更新类

余额

---

首先，调用本地副本；同时在作用域中有两个同名的变量是令人困惑的。然后，在方法末尾，确保将该值赋回类变量

balance

问题在于

updateBal

方法

您已经声明了一个

余额

类变量，但是您声明了另一个

余额

变量作为该方法的本地变量。您成功地更新了本地

余额

，但没有更新类

余额

首先，调用您的本地副本；同时在作用域中有两个同名的变量是令人困惑的。然后，在方法末尾，确保将该值赋回类变量

balance

更改此行

import java.util.Scanner;

import javax.swing.JOptionPane;

public class HW {

public static void main(String[] args){
    balance = 100;
    boolean goAgain = true;
    while (goAgain == true){
        checkGuess(getGuess(), getBet(balance));
        goAgain = goAgain();
    }
}

public static String getGuess(){
    Scanner in = new Scanner(System.in);
    String guess = null;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Guess: (H/T)");
        guess = in.next();
        if (guess.equals("H") || guess.equals("T")){
            validInput = true;
        } else {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + guess);
        }
    }
    return guess;
}

public static double getBet(double balance){
    Scanner in = new Scanner(System.in);
    String betInput = null;
    double betParsed = 0;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Bet? You have: $" + balance);
        betInput = in.next();
        try {
            betParsed = Double.parseDouble(betInput);
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betInput);
        }
        if (betParsed > balance || betParsed <= 0){
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betParsed);
        } else {
            validInput = true;
        }
    }
    return betParsed;
}
public static boolean checkGuess(String getGuess, double getBet){
    double num = Math.round(Math.random()*10);
    boolean correctSide = false;
    if (num <=5 && getGuess.equals("H")){
        correctSide = true;
    } else if (num >=6 && getGuess.equals("T")){
        correctSide = true;
    } else {
        correctSide = false;
    }
    updateBal(correctSide, getBet);
    return correctSide;
}
public static double updateBal(boolean correctSide, double getBet){
    double balance = getBal();
    if (correctSide == true){
        balance = getBet * 2 + balance;
        System.out.println("Correct. Your balance is now $" + balance);
    } else {
        balance = balance - getBet;
        System.out.println("Incorrect. Your balance is now $" + balance);
    }
    return balance;
}
public static boolean goAgain(){
    Scanner in = new Scanner(System.in);
    boolean validInput = false;
    String retryInput = null;
    while (validInput == false){
        System.out.println("Go again? (Y/N)");
        retryInput = in.next();
        if (retryInput.equals("Y") || retryInput.equals("N")){
            validInput = true;
        } else {
            JOptionPane.showInputDialog("Invalid Input: " + retryInput);
        }
    }
    if (retryInput.equals("Y")){
        return true;
    } else {
        System.out.println("You ended with: $" + getBal());
        return false;
    }
}
private static double balance;

public static double getBal() {
  return balance;
}
}

this.balance = updateBal(correctSide, getBet);

到

为什么?

因为在您的

updateBal

方法中，您使用这一行

import java.util.Scanner;

import javax.swing.JOptionPane;

public class HW {

public static void main(String[] args){
    balance = 100;
    boolean goAgain = true;
    while (goAgain == true){
        checkGuess(getGuess(), getBet(balance));
        goAgain = goAgain();
    }
}

public static String getGuess(){
    Scanner in = new Scanner(System.in);
    String guess = null;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Guess: (H/T)");
        guess = in.next();
        if (guess.equals("H") || guess.equals("T")){
            validInput = true;
        } else {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + guess);
        }
    }
    return guess;
}

public static double getBet(double balance){
    Scanner in = new Scanner(System.in);
    String betInput = null;
    double betParsed = 0;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Bet? You have: $" + balance);
        betInput = in.next();
        try {
            betParsed = Double.parseDouble(betInput);
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betInput);
        }
        if (betParsed > balance || betParsed <= 0){
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betParsed);
        } else {
            validInput = true;
        }
    }
    return betParsed;
}
public static boolean checkGuess(String getGuess, double getBet){
    double num = Math.round(Math.random()*10);
    boolean correctSide = false;
    if (num <=5 && getGuess.equals("H")){
        correctSide = true;
    } else if (num >=6 && getGuess.equals("T")){
        correctSide = true;
    } else {
        correctSide = false;
    }
    updateBal(correctSide, getBet);
    return correctSide;
}
public static double updateBal(boolean correctSide, double getBet){
    double balance = getBal();
    if (correctSide == true){
        balance = getBet * 2 + balance;
        System.out.println("Correct. Your balance is now $" + balance);
    } else {
        balance = balance - getBet;
        System.out.println("Incorrect. Your balance is now $" + balance);
    }
    return balance;
}
public static boolean goAgain(){
    Scanner in = new Scanner(System.in);
    boolean validInput = false;
    String retryInput = null;
    while (validInput == false){
        System.out.println("Go again? (Y/N)");
        retryInput = in.next();
        if (retryInput.equals("Y") || retryInput.equals("N")){
            validInput = true;
        } else {
            JOptionPane.showInputDialog("Invalid Input: " + retryInput);
        }
    }
    if (retryInput.equals("Y")){
        return true;
    } else {
        System.out.println("You ended with: $" + getBal());
        return false;
    }
}
private static double balance;

public static double getBal() {
  return balance;
}
}

this.balance = updateBal(correctSide, getBet);

它将类变量

balance

的值复制到局部变量

balance

中。当

updateBal

方法结束时，此局部变量将被删除。如果类变量和局部变量具有相同的名称，默认选项是使用局部变量。 您可以通过“this”强制java使用类变量

例如，您可以将方法

updateBal

更改为此，这样就不必返回任何值：

double balance = getBal();

因为没有称为“balance”的局部变量，所以选择了类变量“balance”

---

顺便说一句：解决这个问题的正确方法是创建新类“Poker”，并在main方法中创建这个类的实例。

更改这一行

import java.util.Scanner;

import javax.swing.JOptionPane;

public class HW {

public static void main(String[] args){
    balance = 100;
    boolean goAgain = true;
    while (goAgain == true){
        checkGuess(getGuess(), getBet(balance));
        goAgain = goAgain();
    }
}

public static String getGuess(){
    Scanner in = new Scanner(System.in);
    String guess = null;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Guess: (H/T)");
        guess = in.next();
        if (guess.equals("H") || guess.equals("T")){
            validInput = true;
        } else {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + guess);
        }
    }
    return guess;
}

public static double getBet(double balance){
    Scanner in = new Scanner(System.in);
    String betInput = null;
    double betParsed = 0;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Bet? You have: $" + balance);
        betInput = in.next();
        try {
            betParsed = Double.parseDouble(betInput);
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betInput);
        }
        if (betParsed > balance || betParsed <= 0){
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betParsed);
        } else {
            validInput = true;
        }
    }
    return betParsed;
}
public static boolean checkGuess(String getGuess, double getBet){
    double num = Math.round(Math.random()*10);
    boolean correctSide = false;
    if (num <=5 && getGuess.equals("H")){
        correctSide = true;
    } else if (num >=6 && getGuess.equals("T")){
        correctSide = true;
    } else {
        correctSide = false;
    }
    updateBal(correctSide, getBet);
    return correctSide;
}
public static double updateBal(boolean correctSide, double getBet){
    double balance = getBal();
    if (correctSide == true){
        balance = getBet * 2 + balance;
        System.out.println("Correct. Your balance is now $" + balance);
    } else {
        balance = balance - getBet;
        System.out.println("Incorrect. Your balance is now $" + balance);
    }
    return balance;
}
public static boolean goAgain(){
    Scanner in = new Scanner(System.in);
    boolean validInput = false;
    String retryInput = null;
    while (validInput == false){
        System.out.println("Go again? (Y/N)");
        retryInput = in.next();
        if (retryInput.equals("Y") || retryInput.equals("N")){
            validInput = true;
        } else {
            JOptionPane.showInputDialog("Invalid Input: " + retryInput);
        }
    }
    if (retryInput.equals("Y")){
        return true;
    } else {
        System.out.println("You ended with: $" + getBal());
        return false;
    }
}
private static double balance;

public static double getBal() {
  return balance;
}
}

this.balance = updateBal(correctSide, getBet);

到

为什么?

因为在您的

updateBal

方法中，您使用这一行

import java.util.Scanner;

import javax.swing.JOptionPane;

public class HW {

public static void main(String[] args){
    balance = 100;
    boolean goAgain = true;
    while (goAgain == true){
        checkGuess(getGuess(), getBet(balance));
        goAgain = goAgain();
    }
}

public static String getGuess(){
    Scanner in = new Scanner(System.in);
    String guess = null;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Guess: (H/T)");
        guess = in.next();
        if (guess.equals("H") || guess.equals("T")){
            validInput = true;
        } else {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + guess);
        }
    }
    return guess;
}

public static double getBet(double balance){
    Scanner in = new Scanner(System.in);
    String betInput = null;
    double betParsed = 0;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Bet? You have: $" + balance);
        betInput = in.next();
        try {
            betParsed = Double.parseDouble(betInput);
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betInput);
        }
        if (betParsed > balance || betParsed <= 0){
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betParsed);
        } else {
            validInput = true;
        }
    }
    return betParsed;
}
public static boolean checkGuess(String getGuess, double getBet){
    double num = Math.round(Math.random()*10);
    boolean correctSide = false;
    if (num <=5 && getGuess.equals("H")){
        correctSide = true;
    } else if (num >=6 && getGuess.equals("T")){
        correctSide = true;
    } else {
        correctSide = false;
    }
    updateBal(correctSide, getBet);
    return correctSide;
}
public static double updateBal(boolean correctSide, double getBet){
    double balance = getBal();
    if (correctSide == true){
        balance = getBet * 2 + balance;
        System.out.println("Correct. Your balance is now $" + balance);
    } else {
        balance = balance - getBet;
        System.out.println("Incorrect. Your balance is now $" + balance);
    }
    return balance;
}
public static boolean goAgain(){
    Scanner in = new Scanner(System.in);
    boolean validInput = false;
    String retryInput = null;
    while (validInput == false){
        System.out.println("Go again? (Y/N)");
        retryInput = in.next();
        if (retryInput.equals("Y") || retryInput.equals("N")){
            validInput = true;
        } else {
            JOptionPane.showInputDialog("Invalid Input: " + retryInput);
        }
    }
    if (retryInput.equals("Y")){
        return true;
    } else {
        System.out.println("You ended with: $" + getBal());
        return false;
    }
}
private static double balance;

public static double getBal() {
  return balance;
}
}

this.balance = updateBal(correctSide, getBet);

它将类变量

balance

的值复制到局部变量

balance

中。当

updateBal

方法结束时，此局部变量将被删除。如果类变量和局部变量具有相同的名称，默认选项是使用局部变量。 您可以通过“this”强制java使用类变量

例如，您可以将方法

updateBal

更改为此，这样就不必返回任何值：

double balance = getBal();

因为没有称为“balance”的局部变量，所以选择了类变量“balance”

---

顺便说一句：解决这个问题的正确方法是创建新类“Poker”，并在main方法中创建这个类的实例。

更改这一行

import java.util.Scanner;

import javax.swing.JOptionPane;

public class HW {

public static void main(String[] args){
    balance = 100;
    boolean goAgain = true;
    while (goAgain == true){
        checkGuess(getGuess(), getBet(balance));
        goAgain = goAgain();
    }
}

public static String getGuess(){
    Scanner in = new Scanner(System.in);
    String guess = null;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Guess: (H/T)");
        guess = in.next();
        if (guess.equals("H") || guess.equals("T")){
            validInput = true;
        } else {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + guess);
        }
    }
    return guess;
}

public static double getBet(double balance){
    Scanner in = new Scanner(System.in);
    String betInput = null;
    double betParsed = 0;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Bet? You have: $" + balance);
        betInput = in.next();
        try {
            betParsed = Double.parseDouble(betInput);
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betInput);
        }
        if (betParsed > balance || betParsed <= 0){
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betParsed);
        } else {
            validInput = true;
        }
    }
    return betParsed;
}
public static boolean checkGuess(String getGuess, double getBet){
    double num = Math.round(Math.random()*10);
    boolean correctSide = false;
    if (num <=5 && getGuess.equals("H")){
        correctSide = true;
    } else if (num >=6 && getGuess.equals("T")){
        correctSide = true;
    } else {
        correctSide = false;
    }
    updateBal(correctSide, getBet);
    return correctSide;
}
public static double updateBal(boolean correctSide, double getBet){
    double balance = getBal();
    if (correctSide == true){
        balance = getBet * 2 + balance;
        System.out.println("Correct. Your balance is now $" + balance);
    } else {
        balance = balance - getBet;
        System.out.println("Incorrect. Your balance is now $" + balance);
    }
    return balance;
}
public static boolean goAgain(){
    Scanner in = new Scanner(System.in);
    boolean validInput = false;
    String retryInput = null;
    while (validInput == false){
        System.out.println("Go again? (Y/N)");
        retryInput = in.next();
        if (retryInput.equals("Y") || retryInput.equals("N")){
            validInput = true;
        } else {
            JOptionPane.showInputDialog("Invalid Input: " + retryInput);
        }
    }
    if (retryInput.equals("Y")){
        return true;
    } else {
        System.out.println("You ended with: $" + getBal());
        return false;
    }
}
private static double balance;

public static double getBal() {
  return balance;
}
}

this.balance = updateBal(correctSide, getBet);

到

为什么?

因为在您的

updateBal

方法中，您使用这一行

import java.util.Scanner;

import javax.swing.JOptionPane;

public class HW {

public static void main(String[] args){
    balance = 100;
    boolean goAgain = true;
    while (goAgain == true){
        checkGuess(getGuess(), getBet(balance));
        goAgain = goAgain();
    }
}

public static String getGuess(){
    Scanner in = new Scanner(System.in);
    String guess = null;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Guess: (H/T)");
        guess = in.next();
        if (guess.equals("H") || guess.equals("T")){
            validInput = true;
        } else {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + guess);
        }
    }
    return guess;
}

public static double getBet(double balance){
    Scanner in = new Scanner(System.in);
    String betInput = null;
    double betParsed = 0;
    boolean validInput = false;
    while (validInput == false){
        System.out.println("Bet? You have: $" + balance);
        betInput = in.next();
        try {
            betParsed = Double.parseDouble(betInput);
        } catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betInput);
        }
        if (betParsed > balance || betParsed <= 0){
            JOptionPane.showMessageDialog(null, "Invalid Input: " + betParsed);
        } else {
            validInput = true;
        }
    }
    return betParsed;
}
public static boolean checkGuess(String getGuess, double getBet){
    double num = Math.round(Math.random()*10);
    boolean correctSide = false;
    if (num <=5 && getGuess.equals("H")){
        correctSide = true;
    } else if (num >=6 && getGuess.equals("T")){
        correctSide = true;
    } else {
        correctSide = false;
    }
    updateBal(correctSide, getBet);
    return correctSide;
}
public static double updateBal(boolean correctSide, double getBet){
    double balance = getBal();
    if (correctSide == true){
        balance = getBet * 2 + balance;
        System.out.println("Correct. Your balance is now $" + balance);
    } else {
        balance = balance - getBet;
        System.out.println("Incorrect. Your balance is now $" + balance);
    }
    return balance;
}
public static boolean goAgain(){
    Scanner in = new Scanner(System.in);
    boolean validInput = false;
    String retryInput = null;
    while (validInput == false){
        System.out.println("Go again? (Y/N)");
        retryInput = in.next();
        if (retryInput.equals("Y") || retryInput.equals("N")){
            validInput = true;
        } else {
            JOptionPane.showInputDialog("Invalid Input: " + retryInput);
        }
    }
    if (retryInput.equals("Y")){
        return true;
    } else {
        System.out.println("You ended with: $" + getBal());
        return false;
    }
}
private static double balance;

public static double getBal() {
  return balance;
}
}

this.balance = updateBal(correctSide, getBet);

它将类变量

balance

的值复制到局部变量

balance

中。当

updateBal

方法结束时，此局部变量将被删除。如果类变量和局部变量具有相同的名称，默认选项是使用局部变量。 您可以通过“this”强制java使用类变量

例如，您可以将方法

updateBal

更改为此，这样就不必返回任何值：

double balance = getBal();

因为没有称为“balance”的局部变量，所以选择了类变量“balance”

---

顺便说一句：解决这个问题的正确方法是创建新的类“扑克”