java基础---->java的新特性（一）

Z时代
2024-01-10
分类：综合

java

　　通过简单的实例来感觉一下java7和java8的新特性。当那条唯捷径省略了朝拜者，我便在一滴花露中瞬间彻悟。

一、java7中switch中可以字符串

@Test
public void jdk7Switch() {
    String name = "huhx";
    switch (name) {
        case "huhx":
            System.out.println("name is = " + name);
            break;
        case "linux":
            System.out.println("name is = " + name);
            break;
        default:
            System.out.println("my name is huhx.");
    }
}

二、二进制和数字下划线的分割的支持

@Test
public void jdk7Binary() {
    int bNum = 0b11110001;
    System.out.println(bNum); // 241
    int num = 12_234_34_45;
    System.out.println(num); // 122343445
}

三、关于异常和自动的资源管理

@Test
public void jdk7CatchExceptions() {
    try {
        Integer.parseInt("aa");
    } catch (NumberFormatException | MaxRunTimeException e) {
        e.printStackTrace();
    }
}
@Test
public void jdk7TryWithResource() throws IOException {
    try (BufferedReader reader = new BufferedReader(new FileReader("C:/Users/76801/Desktop/huhx.txt"))) {
        StringBuilder builder = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            builder.append(line + "\n");
        }
        System.out.println(builder.toString());
    }
}

java8代码实例

一、Lambda的简单使用

package com.tomhu.huhx.java8;
import org.junit.Test;
import java.util.function.Function;
/**
 * @Author: huhx
 * @Date: 2017-09-21 上午 9:10
 */
public class LambdaTest {
    @Test
    public void lambdaThread1() {
        Thread thread = new Thread(() -> {
            System.out.println("hello wolrd");
        });
        thread.start();
    }
    @Test
    public void lambaFunction1() {
        // Function是1.8里面的函数式接口
        Function<Integer, String> function1 = new Function<Integer, String>() {
            @Override
            public String apply(Integer integer) {
                return null;
            }
        };
        // lambda expression
        Function<Integer, String> function2 = (t) -> String.valueOf(t);
        // 引用的方式
        Function<Integer, String> function3 = String::valueOf;
    }
}

二、函数式接口

定义一个函数式接口：DefaultFunInterface]

package com.tomhu.huhx.java8;
/**
 * @Author: huhx
 * @Date: 2017-09-21 上午 9:35
 */
public interface DefaultFunInterface {
    default int count() {
        return 1;
    }
    public static int find() {
        return 1;
    }
}

对上述的接口测试：InterfaceSuper

package com.tomhu.huhx.java8;
import org.junit.Test;
/**
 * @Author: huhx
 * @Date: 2017-09-21 上午 9:34
 */
public class InterfaceSuper {
    @Test
    public void defaultMethond() {
        DefaultFunInterface funInterface = new SubDefaultFunClass();
        System.out.println(funInterface.count()); // 1
    }
    // 接口可以直接调用自己的static方法
    @Test
    public void staticMethod() {
        System.out.println(DefaultFunInterface.find()); // 1
    }
}
class SubDefaultFunClass implements DefaultFunInterface {
    @Override
    public int count() {
        return 0;
    }
}

三、java中nio的改进

package com.tomhu.huhx.java8;
import org.junit.Test;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.time.LocalDate;
import java.util.ArrayList;
import java.util.List;
/**
 * @Author: huhx
 * @Date: 2017-09-21 上午 9:39
 */
public class StreamTest {
    @Test
    public void streamTest1() {
        List<String> stringList = new ArrayList<>();
        stringList.add("linux");
        stringList.add("liuling");
        stringList.add("liuli");
        stringList.add("tomhu");
        stringList.add("zhoucf");
        stringList.stream().filter((s -> s.startsWith("l"))).forEach(System.out::print); // linuxliulingliuli
    }
    @Test
    public void findAllFiles() throws IOException {
        Files.list(new File(".").toPath()).forEach(System.out::println);
    }
    @Test
    public void localDateTest() {
        LocalDate localDate = LocalDate.now(); // 2017-09-21
        System.out.println(localDate);
        localDate = LocalDate.ofYearDay(2017, 333); // 2017-11-29
        System.out.println(localDate);
    }
}

四、更加简单的遍历Collection类型

public void listForEachTest() {
    List<String> lists = Arrays.asList("huhx", "linux", "liuling");
    lists.forEach(item -> {
        if (item.startsWith("l")) {
            System.out.println(item);
        }
    });
    lists.forEach(System.out::println);
    lists.stream().filter(item -> item.contains("l")).forEach(System.out::println);
}
public void mapForEachTest() {
    Map<String, String> map = new HashMap<>();
    map.put("name", "huhx");
    map.put("pass", "1234");
    map.forEach((key, val)-> {
        if (key.equals("name")) {
            System.out.println(val);
        }
    });
}