写出优质Java代码的4个技巧

public void processIntegers(List<Integer> integers) {

    for (Integer value: integers) {
        for (int i = integers.size() - 1; i >= 0; i--) {
            value += integers.get(i);
        }
    }
}

public class HttpResponseCodes {
    public static final int OK = 200;
    public static final int NOT_FOUND = 404;
    public static final int FORBIDDEN = 403;
}
if (getHttpResponse().getStatusCode() == HttpResponseCodes.OK) {
    // Do something if the response code is OK 
}

public class HttpResponseHandler {
    public static void printMessage(int statusCode) {
        System.out.println("Recieved status of " + statusCode); 
    }
}
HttpResponseHandler.printMessage(15000);

public class HttpResponseCodes {
    public static final int OK = 200;
    public static final int NOT_FOUND = 404;
    public static final int FORBIDDEN = 403;
    public static boolean isSuccess(int statusCode) {
        return statusCode >= 200 && statusCode < 300; 
    }
}
if (HttpResponseCodes.isSuccess(getHttpResponse().getStatusCode())) {
    // Do something if the response code is a success code 
}

public enum HttpResponseCodes {
    OK(200),
    FORBIDDEN(403),
    NOT_FOUND(404);
    private final int code; 
    HttpResponseCodes(int code) {
        this.code = code;
    }
    public int getCode() {
        return code;
    }
    public boolean isSuccess() {
        return code >= 200 && code < 300;
    }
}
if (getHttpResponse().getStatusCode().isSuccess()) {
    // Do something if the response code is a success code 
}

public class HttpResponseHandler {
    public static void printMessage(HttpResponseCode statusCode) {
        System.out.println("Recieved status of " + statusCode.getCode()); 
    }
}
HttpResponseHandler.printMessage(HttpResponseCode.OK);

public class NumericConstants {
    public static final double PI = 3.14;
    public static final double UNIT_CIRCLE_AREA = PI * PI;
}
public class Rug {
    private final double area;
    public class Run(double area) {
        this.area = area;
    }
    public double getCost() {
        return area * 2;
    }
}
// Create a carpet that is 4 feet in diameter (radius of 2 feet)
Rug fourFootRug = new Rug(2 * NumericConstants.UNIT_CIRCLE_AREA);

public class Purchase {
    private long id;
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
}

Purchase originalPurchase = new Purchase();
Purchase updatedPurchase = new Purchase();
if (originalPurchase.getId() == updatedPurchase.getId()) {
    // Execute some logic for equal purchases 
}

public class Purchase {
    private long id;
    public boolean isSame(Purchase other) {
        return getId() == other.gerId();   
    }
}

public boolean equals(Object obj) {
    return (this == obj);
}

public class Purchase {
    private long id;
    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    @Override
    public boolean equals(Object other) {
        if (this == other) {
            return true;
        }
        else if (!(other instanceof Purchase)) {
            return false;
        }
        else {
            return ((Purchase) other).getId() == getId();
        }
    }
}

Purchase originalPurchase = new Purchase();
Purchase updatedPurchase = new Purchase();
if (originalPurchase.equals(updatedPurchase)) {
    // Execute some logic for equal purchases 
}

List<Purchase> purchases = new ArrayList<>();
purchases.add(originalPurchase);
purchases.contains(updatedPurchase); // True

if (originalPurchase == updatedPurchase) {
    // The two objects are the same objects in memory 
}

public enum BankAccountType {
    CHECKING,
    SAVINGS,
    CERTIFICATE_OF_DEPOSIT;
}
public class BankAccount {
    private final BankAccountType type;
    public BankAccount(BankAccountType type) {
        this.type = type;
    }
    public double getInterestRate() {
        switch(type) {
            case CHECKING:
                return 0.03; // 3%
            case SAVINGS:
                return 0.04; // 4%
            case CERTIFICATE_OF_DEPOSIT:
                return 0.05; // 5%
            default:
                throw new UnsupportedOperationException();
        }
    }
    public boolean supportsDeposits() {
        switch(type) {
            case CHECKING:
                return true;
            case SAVINGS:
                return true;
            case CERTIFICATE_OF_DEPOSIT:
                return false;
            default:
                throw new UnsupportedOperationException();
        }
    }
}

public interface BankAccount {
    public double getInterestRate();
    public boolean supportsDeposits();
}
public class CheckingAccount implements BankAccount {
    @Override
    public double getIntestRate() {
        return 0.03;
    }
    @Override
    public boolean supportsDeposits() {
        return true;
    }
}
public class SavingsAccount implements BankAccount {
    @Override
    public double getIntestRate() {
        return 0.04;
    }
    @Override
    public boolean supportsDeposits() {
        return true;
    }
}
public class CertificateOfDepositAccount implements BankAccount {
    @Override
    public double getIntestRate() {
        return 0.05;
    }
    @Override
    public boolean supportsDeposits() {
        return false;
    }
}

BankAccount checkingAccount = new BankAccount(BankAccountType.CHECKING);
System.out.println(checkingAccount.getInterestRate()); // Output: 0.03

BankAccount checkingAccount = new CheckingAccount();
System.out.println(checkingAccount.getInterestRate()); // Output: 0.03

public class ConditionalAccountFactory {
    public static BankAccount createCheckingAccount() {
         return new BankAccount(BankAccountType.CHECKING);
    }
}
public class PolymorphicAccountFactory {
    public static BankAccount createCheckingAccount() {
         return new CheckingAccount();
    }
}
// In both cases, we create the accounts using a factory
BankAccount conditionalCheckingAccount = ConditionalAccountFactory.createCheckingAccount();
BankAccount polymorphicCheckingAccount = PolymorphicAccountFactory.createCheckingAccount();
// In both cases, the call to obtain the interest rate is the same
System.out.println(conditionalCheckingAccount.getInterestRate()); // Output: 0.03
System.out.println(polymorphicCheckingAccount.getInterestRate()); // Output: 0.03