beginner.AboutObjects Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of java-koans Show documentation

There is a newer version: 1.2.0

package beginner;

import com.sandwich.koan.Koan;

import java.text.MessageFormat;
import java.util.ArrayList;
import java.util.List;

import static com.sandwich.koan.constant.KoanConstants.__;
import static com.sandwich.util.Assert.assertEquals;

public class AboutObjects {

    @Koan
    public void newObjectInstancesCanBeCreatedDirectly() {
        assertEquals(new Object() instanceof Object, __);
    }

    @Koan
    public void allClassesInheritFromObject() {
        class Foo {
        }

        Class[] ancestors = getAncestors(new Foo());
        assertEquals(ancestors[0], __);
        assertEquals(ancestors[1], __);
    }

    @Koan
    public void objectToString() {
        Object object = new Object();
        // TODO: Why is it best practice to ALWAYS override toString?
        String expectedToString = MessageFormat.format("{0}@{1}", Object.class.getName(), Integer.toHexString(object.hashCode()));
        assertEquals(expectedToString, __); // hint: object.toString()
    }

    @Koan
    public void toStringConcatenates() {
        final String string = "ha";
        Object object = new Object() {
            @Override
            public String toString() {
                return string;
            }
        };
        assertEquals(string + object, __);
    }

    @Koan
    public void toStringIsTestedForNullWhenInvokedImplicitly() {
        String string = "string";
        assertEquals(string + null, __);
    }

    private Class[] getAncestors(Object object) {
        List> ancestors = new ArrayList>();
        Class clazz = object.getClass();
        while (clazz != null) {
            ancestors.add(clazz);
            clazz = clazz.getSuperclass();
        }
        return ancestors.toArray(new Class[]{});
    }

}