New features in Java 8

One, function-type programming

1. Lambda expression

parameter values, function body content, for example:

Before Java 8:
New Thread (New Runnable () {
@Override
public void Run () {
System.out.println ("Before Java8, too much code for too little");
}
}). Start ();

Java 8 Way:
New Thread ((), System.out.println ("in Java8, Lambda expression Rocks!"). Start ();

Other usage scenarios are: event handling, event monitoring code, iteration of the list (List.foreach (n-System.out.println (n));)

2. Method reference

Some lambda expressions simply execute a method call. In this case, without a lambda expression, it is easier to refer to the method directly by means of the method name, which is a method reference, a more concise and understandable type of lambda expression.

Arrays.sort (Stringsarray, string::comparetoignorecase);
is equivalent to

Arrays.sort (Stringsarray, (s1,s2)->s1.comparetoignorecase (S2));
shorthand for a method that already exists in a lambda expression directly from a method reference

Ii. Collection of new operations

1. Create a string list by filtering // 创建一个字符串列表，每个字符串长度大于2 List<String> filtered = strList.stream().filter(x -> x.length()> 2 ).collect(Collectors.toList());2. Apply a function to each element of the list // 将字符串换成大写并用逗号链接起来 List<String> G7 = Arrays.asList( "USA" , "Japan" , "France" , "Germany" , "Italy" , "U.K." , "Canada" ); String G7Countries = G7.stream().map(x -> x.toUpperCase()).collect(Collectors.joining( ", " )); System.out.println(G7Countries);3. Remove duplicate elements

List<Integer> numbers = Arrays.asList(9, 10, 3, 4, 7, 3, 4);

List<Integer> distinct = numbers.stream().map( i -> i*i).distinct().collect(Collectors.toList());

4. Calculate the maximum, minimum, sum, and average values of the SET elements

List<Integer> primes = Arrays.asList(2, 3, 5, 7, 11, 13, 17, 19, 23, 29);

IntSummaryStatistics stats = primes.stream().mapToInt((x) -> x).summaryStatistics();

System.out.println("Highest prime number in List : "+ stats.getMax());

System.out.println("Lowest prime number in List : "+ stats.getMin());

System.out.println("Sum of all prime numbers : "+ stats.getSum());

System.out.println("Average of all prime numbers : "+ stats.getAverage());

New features in Java 8