HelloGroovy3.groovy

// Show some new features of Groovy3
// The complete new feature list can be found at:
// https://github.com/danielsun1106/groovy-parser
@groovy.transform.CompileStatic
def helloGroovy3() {
    File f = new File("D:/hello-groovy${1 + 2}.txt")

    try (Writer out = new FileWriter(f)) { // try-with-resources
        out <<
            ['hello', 'groovy3', 'Hello', 'Groovy3'].stream()
                .filter(e -> !Character.isLowerCase(e[0] as char)) // lambda expression
                .map(String::toUpperCase) // method reference
                .toArray(String[]::new)   // constructor reference
                .join(', ')
    }
    
    assert 'HELLO, GROOVY3' == f.text
}

helloGroovy3()