NewFeatureTest.java

package study.java.jdks.version1_7.new_feature;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;


public class NewFeatureTest {

	public static void main(String[] args) throws Exception{
		// 1.二进制字面量
		byte nByte=(byte)0b0101;
		short nShort = (short)0B0010;
		int nInt = 0b1111;
		long nLong = 0B0100;
		System.out.println(nByte);
		System.out.println(nShort);
		System.out.println(nInt);
		System.out.println(nLong);
		
		// 2.数字字面量允许使用下划线
		int i = 1_234_576;
		System.out.println(i);
		float f = 1_234.55_66_77_88f;
		System.out.println(f);
		
		// 3.switch语句允许使用字符串
		String s = "red";
		switch (s) {
		case "yellow":
			System.out.println("this is yellow");
			break;
		case "red":
			System.out.println("tihs is red");
			break;
		case "green":
			System.out.println("this is green");
			break;
		default:
			System.out.println("end");

		}
		
		// 4.泛型实例的创建可以通过类型推断来简化
		List<String> list = new ArrayList<>();
		
		// 7.Catch多个Exception,throw exception改进了类型检测
		try{
			File a= new File("xx.txt");
			FileWriter fw = new FileWriter(a);
		} catch(IOException|RuntimeException e) {
			System.out.println(e);
			throw e;
		}
	
	}
	
	public static <T> void addToList(List<T> listArg,T element) {
		listArg.add(element);
	}
	
	// 5.在可变参数方法中传递非具体化参数,改进编译警告和错误
	public static <T> void addToList(List<T> listArg,T...elements) {
		for(T x:elements) {
			listArg.add(x);
		}
	}
	
	public static void testHeapPollution() {
	    List l = new ArrayList<Number>();
	    List<String> ls = l;       // unchecked warning
	    l.add(0, new Integer(42)); // another unchecked warning
	    String s = ls.get(0);      // ClassCastException is thrown
	}
	
	// 6.try-with-resources语句
	public static String readFirstLineFromFile(String path) throws IOException {
		String result = null;
		try{
			BufferedReader br = new BufferedReader(new FileReader(path));
			result = br.readLine();
		} catch(Exception e) {
			
		} finally{
			return result;
		}
	}
}