See this for detailed description.

In Java, parameters are always passed by value. For example, following program prints i = 10, j = 20.

// Test.java
class Test {
// swap() doesn't swap i and j
public static void swap(Integer i, Integer j) {
Integer temp = new Integer(i);
i = j;
j = temp;
}
public static void main(String[] args) {
Integer i = new Integer(10);
Integer j = new Integer(20);
swap(i, j);
System.out.println("i = " + i + ", j = " + j);
}
}