提高生产力:这10个Lambda表达式必须掌握

发布时间:2024-02-04 14:21:28
 

使用Lambda表达式进行集合遍历

❌ 未使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
for (string fruit : list) {
    System.out.println(fruit);
}

✅ 使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
list.forEach(fruit -> System.out.println(fruit));

使用Lambda表达式进行排序

❌ 未使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
Collections.sort(list, new Comparator() {
    public int compare(String s1, String s2) {
        return s1.compareTo(s2);
    }
});

✅ 使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
Collections.sort(list, (s1, s2) -> s1.compareTo(s2));

使用Lambda表达式进行过滤

❌ 未使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
List filteredList = new ArrayList();
for (String fruit : list) {
    if (fruit.startsWith("a")) {
        filteredList.add(fruit);
    }
}

✅ 使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
List filteredList = list.stream().filter(fruit -> fruit.startsWith("a"))
								.collect(Collectors.toList());

使用Lambda表达式进行映射

❌ 未使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
List lengths = new ArrayList();
for (String fruit : list) {
    lengths.add(fruit.length());
}

✅ 使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
List lengths = list.stream()
                	.map(fruit -> fruit.length())
                	.collect(Collectors.toList());

使用Lambda表达式进行归约

❌ 未使用Lambda表达式:

List list = Arrays.asList(1, 2, 3, 4, 5);
int sum = 0;
for (int i : list) {
	sum += i;
}

✅ 使用Lambda表达式:

List list = Arrays.asList(1, 2, 3, 4, 5);
int sum = list.stream().reduce(0, (a, b) -> a + b);

使用Lambda表达式进行分组

❌ 未使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
Map<Integer, List> grouped = new HashMap<Integer, List>();
for (String fruit : list) {
    int length = fruit.length();
    if (!grouped.containsKey(length)) {
        grouped.put(length, new ArrayList());
    }
    grouped.get(length).add(fruit);
}

✅ 使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
Map<Integer, List> grouped = list.stream()
				.collect(Collectors.groupingBy(fruit -> fruit.length()));

使用Lambda表达式进行函数式接口的实现

❌ 未使用Lambda表达式:

public interface MyInterface {
    public void doSomething(String input); 
}

MyInterface myObject = new MyInterface() {
	public void doSomething(String input) {
		System.out.println(input);
	}
};

myObject.doSomething("Hello World");

✅ 使用Lambda表达式:

MyInterface myObject = input -> System.out.println(input);
myObject.doSomething("Hello World");

使用Lambda表达式进行线程的创建

❌ 未使用Lambda表达式:

Thread thread = new Thread(new Runnable() {
    public void run() {
    	System.out.println("Thread is running.");
    }
});
thread.start();

✅ 使用Lambda表达式:

Thread thread = new Thread(() -> System.out.println("Thread is running."));
thread.start();

使用Lambda表达式进行Optional的操作

❌ 未使用Lambda表达式:

String str = "Hello World";
if (str != null) {
	System.out.println(str.toUpperCase());
}

✅ 使用Lambda表达式:

Optional str = Optional.ofNullable("Hello World");
str.map(String::toUpperCase)
	.ifPresent(System.out::println);

使用Lambda表达式进行Stream的流水线操作

❌ 未使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
List filteredList = new ArrayList();
for (String fruit : list) {
    if (fruit.startsWith("a")) {
        filteredList.add(fruit.toUpperCase());
    }
}
Collections.sort(filteredList);

✅ 使用Lambda表达式:

List list = Arrays.asList("apple", "banana", "orange");
List filteredList = list.stream().filter(fruit -> fruit.startsWith("a"))
								.map(String::toUpperCase)
								.sorted()
								.collect(Collectors.toList());

 
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