Short-Circuiting, and the Null Check That Leans On It

A condition that reads like it does two things and sometimes only does one. It is the reason a null check works at all.

java

if (name != null && name.length() > 3) {
    System.out.println("long enough");
}

If name is null, the left side is false. && can already answer the whole question — false and anything is false — so it never evaluates the right side, and name.length() is never called on nothing.

When each operator stops early
Operator	Stops when the left side is	Because
`&&`	false	Nothing on the right can make it true
`\|\|`	true	Nothing on the right can make it false
`&`	Never	Both sides are always evaluated
`\|`	Never	Both sides are always evaluated

Short-circuiting means the order of your conditions is part of their meaning. Put the cheap test and the guard on the left, and the expensive or unsafe one on the right.

Java
JVM