static Keyword in Java

What does static mean

The static keyword makes a variable or method belong to the class itself, not to individual objects. A static member is shared by all objects, and you can use it through the class name without creating any object.

Static variables

class Counter {
    static int count = 0;   // shared by all objects
    Counter() { count++; }  // increases the shared count
}
// use:
new Counter(); new Counter(); new Counter();
System.out.println(Counter.count);

There is only one count, shared by every object. Each new object increases the same variable, so it correctly counts how many were created — accessed via the class name.

Static methods

class MathUtil {
    static int square(int n) {
        return n * n;
    }
}
// call without an object:
System.out.println(MathUtil.square(5));

A static method is called on the class, not an object — MathUtil.square(5). This is why utility methods and main are static.

Static blocks

class Config {
    static String appName;
    static {
        appName = "CodingEasily";   // runs once at class load
        System.out.println("Static block ran");
    }
}

A static { } block runs once when the class is first loaded, before any object exists. It is handy for setting up static variables that need more than a simple value.

static vs instance

When to use static

• Shared data that all objects use, like a counter or a constant.
• Utility methods that do not depend on object data, like Math.max.
• Constants, often combined as static final.

Use static when something belongs to the class as a whole, not to one object.

Common mistakes

• Using instance variables in a static method. A static method has no object, so it cannot.
• Expecting per-object copies of a static variable. There is only one, shared by all.
• Overusing static. Too much static breaks object-oriented design; use it only when shared.
• Calling static via an object. It works but is confusing — call it via the class name.

Summary

• static makes a member belong to the class, not each object.
• A static variable is one shared copy across all objects.
• A static method is called on the class, without an object.
• A static block runs once when the class loads.
• Use static for shared data, utility methods and constants.

Next, control visibility with access modifiers, or organise code with Java methods.