Lambda表达式if-else语句

Question

Hello I Just started learning Lambda expressions, how do I write this with Lambda expressions?

  public static void greaterThanFive(String str){
    if(str.length() > 5){
        System.out.println("String length is larger than 5 ");
    }else{
        System.err.println("String length less than 5");
    }

if it was just an, if statement I could just do this:

Predicate<String> greaterThanFive = (s)-> s.length() > 5;

But I can't really figure out when it's an if-else statement.

Answer 1

Comparator<String> c = (String first, String second) -> {
if (first.length() < second.length()) return -1;
else if (first.length() > second.length()) return 1;
else return 0;
};

I believe this answers your question. For more info, read Java8 for really impatient. Its a really good book.

Answer 2

Using blocks, you can create lambda expressions that have multiple statements or big statements (like an if-else). Example:

new Thread( () -> { // Btw, you can use java.lang.Runnable with a lambda
    System.out.println("A wild NEW THREAD appeared!"); // :)
    try {
        Thread.sleep(5000);
    } catch (InterruptedException e) {}
    System.out.println("Enemy NEW THREAD ran away!");
});

This means all you have to do is to enclose that if-else in the block of a lambda:

Consumer<String> greaterThanFive = (s) -> {
    // ...
};

Note that there's a semicolon after the block.