Java8が好きになる話（StreamAPIの話はしない） その2 Optional#map - Qiita

public static class Struct1 { private final Struct2 value; public Struct1(Struct2 value) { this.value = value; } public Struct2 getValue() { return this.value; } } public static class Struct2 { private final Struct3 value; public Struct2(Struct3 value) { this.value = value; } public Struct3 getValue() { return this.value; } } public static class Struct3 { private final String value; public Struct3