Eclipse上的Gradle，钻石操作员无法识别？

Question

我有一段代码，当我在Eclipse上运行它时（没有Gradle，它运行良好），我正在迁移到Gradle，但是当我使用Eclipse插件或尝试运行它时，尽管命令行我有钻石运算符的问题。

例如，对于这个类：

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())); 
} 

}

我得到错误类型的illegat开始：

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

我知道钻石操作者可以自JDK7使用有泛型的类型推理，所以我很困惑，为什么我得到这个错误。你能帮我修好吗？

在此先感谢

Answer 1

除非你指定的Java版本的使用，将摇篮在使用中使用JVM的当前版本的编译代码。如果您看到有关钻石操作员的错误消息，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，请使另一个版本处于活动状态）。

它几乎总是通过添加这些行到你的build.gradle文件中明确指定的版本是一个好主意：

sourceCompatibility = 1.7 
targetCompatibility = 1.7 

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