null in ABAP and nullpointer in Java_JAVA_编程开发_程序员俱乐部

ABAP

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Java

monospace; font-size: inherit; background-color: inherit;" class="language-text">class Outer {
    Nested nested;
    Nested getNested() {
        return nested;
    }
    
    public Outer(){
    	// nested = new Nested();
    }
}
class Nested {
    Inner inner;
    Inner getInner() {
        return inner;
    }
    
    public Nested() {
    	// inner = new Inner();
    }
}

class Inner {
    String foo = "Jerry";
    String getFoo() {
        return foo;
    }
}

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为了打印嵌套层数很深的foo：

# 2B青年的写法

public void test1(){
		Outer outer = new Outer();
		if (outer != null && outer.nested != null && outer.nested.inner != null) {
		    System.out.println(outer.nested.inner.foo);
		}
	}

?

# 文艺青年的写法

public void test2(){
		Optional.of(new Outer()).map(Outer::getNested).map(Nested::getInner).map(Inner::getFoo)
			.ifPresent(System.out::println);
	}

More discussion of ABAP, Java and JavaScript could be found from my Wechat article Jerry的ABAP, Java和JavaScript乱炖:?Jerry的ABAP, Java和JavaScript乱炖