How do I use the “return” keyword in Java?

By Wayan in Basic, Core API 5 Comments

The return keyword is used to return from a method when its execution is complete. When a return statement is reached in a method, the program returns to the code that invoked it.

A method can return a value or reference type or does not return a value. If a method does not return a value, the method must be declared void and it doesn’t need to contain a return statement.

If a method declare to return a value, then it must use the return statement within the body of method. The data type of the return value must match the method’s declared return type.

package org.kodejava.basic;

public class ReturnDemo {

    public static void main(String[] args) {
        int z = ReturnDemo.calculate(2, 3);
        System.out.println("z = " + z);

        Dog dog = new Dog("Spaniel", "Doggie");
        System.out.println(dog.getDog());
    }

    public static int calculate(int x, int y) {
        // return an int type value
        return x + y;
    }

    public void print() {
        System.out.println("void method");

        // it does not need to contain a return statement, but it
        // may do so
        return;
    }

    public String getString() {
        return "return String type value";

        // try to execute a statement after return a value will
        // cause a compile-time error.
        //
        // String error = "error";
    }
}

class Dog {
    private String breed;
    private String name;

    Dog(String breed, String name) {
        this.breed = breed;
        this.name = name;
    }

    public Dog getDog() {
        // return Dog type
        return this;
    }

    public String toString() {
        return "breed: " + breed.concat("name: " + name);
    }
}

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5 Comments

  1. I know that || is an or operator when used in an if else, but what about a single | when used in a return? I’ve looked everywhere, but it seems like a single | is completely ignored by google’s search engine 😡

    Here’s an example:

    return removeHalfBit(k) | (flag ? 8 : 0) | (flag1 ? 16 : 0) | (flag2 ? 32 : 0);
    Reply

    • Hi Nick,

      The |, &, ^ are logical operators, but they can also be used as a bitwise operators. As bitwise operators they compare two variables bit by bit and return a variable whose bits have been set based on whether the two variables being compared had respective bits that were either both on (&), one or the other on (|), or exactly one on (^). On means 1 while off means 0.

      For example:

      int a = 10;    // 1010 (binary)
int b = 5;     // 0101
int c = a | b; // 1111
int d = a & b; // 0000

      More:

      Reply

  3. I don’t get what the use of return is. Why can’t we just leave it and have the method automatically return whatever value is obtained by the instructions in the block that is the method body? Were is it useful for a method NOT to return something? And if that is never the case, why bother with return at all? Why not have it be implied.

    Reply

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