今天学习fabric-sdk的时候，看到这样一段代码

// create a gateway connection
		try (Gateway gateway = builder.connect()) {

			// get the network and contract
			Network network = gateway.getNetwork("mychannel");
			Contract contract = network.getContract("fabcar");
			//以下都是对账本进行的操作，并不重要
			byte[] result;
			contract.submitTransaction("createProject", "PROJECT003", "kkkk", "1", "kkksadas", "100","12","time");
			Timestamp current = new Timestamp(System.currentTimeMillis());
			contract.submitTransaction("createContribution","CONTRIBUTION000","1","PROJECT000","100",current+"");
			contract.submitTransaction("updateProject","PROJECT000","100");

			result = contract.evaluateTransaction("queryContributions","CONTRIBUTION000");
			System.out.println(new String(result));
		}

这个try后面加小括号的写法我还是第一次见，原来这是jdk1.7之后的新特性，括号里面的资源，会在try后面大括号里的内容执行完毕后自动释放。官方的注释

我们可以让类继承AutoCloseable接口，然后用使用try-with-resources block，将对象放到小括号里，这样当代码块执行完毕后，就自动释放小括号里的资源了。不过也提到在使用非I/O类对象时，这个东西不是很有必要