Gradle 在 Eclipse 上，菱形运算符无法识别？

Question

我有一个要迁移到 Gradle 的代码，当我运行它在 Eclipse 上时（没有 Gradle 它运行很好），但是当我使用 Eclipse 插件或尝试运行它通过命令行我有钻石运算符的问题。

例如，对于这个 class:

import java.util.SortedSet;

/**
* Holds inventory of currency, calculates balance, makes change.
* Immutable.
*/
public final class Bank {
/**
 * Inventory of currencies for the bank.
 */
private final Inventory<Currency> inventory;

public Inventory<Currency> getInventory() {
    return inventory;
}

/**
 * Calculate the balance (in cents) of the currently held currencies.
 *
 * @return the current balance (in cents)
 */
public long calculateBalance() {
    long balance = 0L;
    for (Currency currency : Currency.values()) {
        balance += currency.getCents() * inventory.quantity(currency);
    }
    return balance;
}

/**
 * Create a bank made up of currencies from this bank that add up as close
 * as possible to the change amount requested.  Exact change is not
 * guaranteed.  It's a good idea to check that the calculated balance is
 * the same as the amount you expect.
 *
 * @param amount the amount of change needed
 * @return a bank of change made from as much currency that could be used
 */
public Bank makeChange(final long amount) {
    long change = amount;
    Bank changeBank = new Bank();
    final SortedSet<Currency> descending = Currency.descending();
    for (Currency largest : descending) {
        int quantity = inventory.quantity(largest);
        final long cents = largest.getCents();
        while (quantity > 0 && change >= cents) {
            change = change - cents;
            quantity = quantity - 1;
            changeBank = changeBank.deposit(largest);
        }
    }
    return changeBank;
}

/**
 * Bank constructor.  Fills out a new Bank with 0 amounts for each currency.
 */
public Bank()
{
    this.inventory = new Inventory <> (Currency.values());
}

/**
 * Private Bank constructor.  Used for returning new, modified instances.
 *
 * @param inventory the new inventory
 */
private Bank(final Inventory<Currency> inventory) {
    this.inventory = new Inventory<>(Currency.values()).add(inventory);
}

/**
 * Deposit the currencies from the incoming Bank into this Bank.
 *
 * @param bank incoming Bank
 * @return new Bank with this Bank's currencies, incoming Bank's currencies
 */
public Bank deposit(final Bank bank) {
    if (bank == null) {
        return this;
    }
    return new Bank(inventory.add(bank.getInventory()));
}

/**
 * Deposit the currency incoming into this Bank.
 *
 * @param currency incoming currency
 * @return new Bank with this Bank's currencies, incoming currency
 */
public Bank deposit(final Currency currency) {
    if (currency == null) {
        return this;
    }
    return new Bank(inventory.add(currency));
}

/**
 * Withdraws the currencies from the passed in Bank from this Bank.  If
 * there aren't enough of any particular currency, set the quantity to 0.
 *
 * @param bank the Bank of currencies to withdraw
 * @return a Bank with the currencies of the passed Bank withdrawn
 */
public Bank withdraw(final Bank bank) {
    if (bank == null) {
        return this;
    }
    return new Bank(inventory.subtract(bank.getInventory()));
}

}

我遇到类型错误的非法启动：

illegal start of type this.inventory <> (Currency.values());
                                      ^

我知道从 JDK7 开始就可以使用菱形运算符对泛型进行类型推断，所以我很困惑为什么会出现这个错误。你能帮我修一下吗？

提前致谢

Answer 1

除非您指定要使用的 Java 版本，否则 Gradle 将使用当前使用的 JVM 版本编译您的代码。如果您看到有关菱形运算符的错误消息，则可能意味着您在命令行上使用的 Java 版本早于 1.7。您需要升级到更高版本（或者如果安装了多个版本，请激活另一个版本）。

通过将这些行添加到您的 build.gradle 文件来明确指定版本几乎总是一个好主意：

sourceCompatibility = 1.7
targetCompatibility = 1.7

参考：https://docs.gradle.org/current/userguide/java_plugin.html

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