builder.java

public class Foo {
    // immutability
    private final int a;
    private final int b;
    private final int c;
    private final int d;
    private final int e;

    public static class Builder {
        private final int a;
        private final int b;

        private int c = 0;
        private int d = 0;
        private int e = 0;

        public Builder(int a, int b){
            this.a = a;
            this.b = b;
        }

        public Builder c(int val) {c = val; return this;}
        public Builder d(int val) {d = val; return this;}
        public Builder e(int val) {e = val; return this;}

        public Foo build() {
            return new Foo(this);
        }
    }

    private Foo(Builder builder) {
        a = builder.a;
        b = builder.b;
        ...
    }
}

Foo foo = new Foo.Builder(10, 2).c(10).d(20).e(30).build();