Class builder example

ComplexValueClass.java

import javax.annotation.Nonnull;

/**
 * @see #withValue1(String)
 */
public class ComplexValueClass {
    private final String value1;
    private final String value2;
    private final String value3;

    private ComplexValueClass(String value1, String value2, String value3) {
        if (value1 == null) throw new IllegalArgumentException("value1 == null");
        if (value2 == null) throw new IllegalArgumentException("value2 == null");
        if (value3 == null) throw new IllegalArgumentException("value3 == null");
        this.value1 = value1;
        this.value2 = value2;
        this.value3 = value3;
    }

    /**
     * Example:<pre>
     *   ComplexValueClass complexClass = ComplexValueClass.withValue1("a").
     *     andValue2("b").
     *     andValue3("c").
     *     build();
     * </pre>
     */
    public static Builder withValue1(@Nonnull String val) {
        return new Builder(val);
    }

    /**
     * Not meant to be used directly.
     * @see ComplexValueClass#withValue1(String)
     */
    public static class Builder {
        private final String value1;

        private Builder(String val) {
            this.value1 = val;
        }

        public Builder2 andValue2(@Nonnull String val) {
            return new Builder2(val);
        }

        public class Builder2 {
            private final String value2;

            private Builder2(String val) {
                this.value2 = val;
            }

            public Builder3 andValue3(@Nonnull String val) {
                return new Factory3(val);
            }

            public class Builder3 {
                private final String value3;

                private Builder3(String val) {
                    this.value3 = val;
                }

                public ComplexValueClass build() {
                    return new ComplexValueClass(value1, value2, value3);
                }
            }
        }
    }
}