一叶望Java7之5特性

一叶观Java7之5特性

一叶观Java7之5特性

liuu

一个类中，尽览Java7的5个新特性，大家找找看，到底是哪几个：

public class ProjectCoinBanker {  private static final Integer ONE_MILLION = 1_000_000;  private static final String RICH_MSG = "You need more than $%,d to be considered rich.";  public static void main(String[] args) throws Exception {System.out.println(String.format(RICH_MSG, ONE_MILLION));String requestType = args[0];String accountId = args[1];switch (requestType) {case "displayBalance":printBalance(accountId);break;case "lastActivityDate" :printLastActivityDate(accountId);break;case "amIRich" :amIRich(accountId);break;case "lastTransactions" :printLastTransactions(accountId, Integer.parseInt(args[2]));break;case "averageDailyBalance" :printAverageDailyBalance(accountId);break;default: break;}  }  private static void printAverageDailyBalance(String accountId) {        String sql = String.format(AVERAGE_DAILY_BALANCE_QUERY, accountId);try (      PreparedStatement s = _conn.prepareStatement(sql);              ResultSet rs = s.executeQuery();             ) {        while (rs.next()) {  //print the average daily balance results                }     } catch (SQLException e) {// handle exception, but no need for finally to close resources                for (Throwable t : e.getSuppressed()) {   System.out.println("Suppressed exception message is " + t.getMessage());}     }  }  private static void printLastTransactions(String accountId, int numberOfTransactions) {List<Transaction> transactions = new ArrayList<>();... handle fetching/printing transactions  }  private static void printBalance(String accountId) {try {BigDecimal balance = getBalance(accountId);//print balance} catch (AccountFrozenException | ComplianceViolationException | AccountClosedException e) {    System.err.println("Please see your local branch for help with your account.");}  }  private static void amIRich(String accountId) {try {BigDecimal balance = getBalance(accountId);//find out if the account holder is rich} catch (AccountFrozenException | ComplianceViolationException | AccountClosedException e) {    System.out.println("Please see your local branch for help with your account.");}  }  private static BigDecimal getBalance(String acccountId)      throws AccountFrozenException, AccountClosedException, ComplianceViolationException {      ... getBalance functionality  }}

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这5个特性是：

数字可由下划线分隔，增强可读性；Switch支持字符串类型，方便啊；catch可同时捕获多种异常，catch大瘦身；范型类型推断，不用重复写范型类型名了；try增加自动释放资源（AutoClosable接口），忘掉嵌try...catch的finally吧；

代码原文及详细解释，见：http://www.javacodegeeks.com/2011/11/java-7-feature-overview.html