Java Method Parameters

Introduction

Java method can accept data from callers via parameters.

The following code creates a method to calculate square for any input integer values. 

int square(int i)  
{  
  return i * i;  
}

square() will return the square of whatever value passed in. 

public class Main {
  public static void main(String args[]) {
    System.out.println(square(2));
    System.out.println(square(10));
  }/* w ww .j a v a  2 s  . c  o  m*/

  static int square(int i) {
    return i * i;
  }

}

The following code shows how to pass in array as parameters. 

// Use an array to pass a variable number of arguments to a method. 
public class Main { 
  static void myTest(int v[]) { 
    System.out.print("Number of args: " + v.length + 
                       " Contents: "); 
 
    for(int x : v) 
      System.out.print(x + " "); 
 
    System.out.println(); //from   ww w  . j  ava 2 s  .  c om
  } 
 
  public static void main(String args[])  
  { 
    // Notice how an array must be created to 
    // hold the arguments. 
    int n1[] = { 10 }; 
    int n2[] = { 1, 2, 3 }; 
    int n3[] = { }; 
 
    myTest(n1); // 1 arg 
    myTest(n2); // 3 args 
    myTest(n3); // no args 
  } 
}

The following code use parameters to set new dimensions of a lego block. 

// uses a parameterized method.
class LegoBlock {
  double width;//from  w w  w. ja  va 2 s . co m
  double height;
  double depth;

  // compute and return volume
  double volume() {
    return width * height * depth;
  }

  // sets dimensions
  void setDim(double w, double h, double d) {
    width = w;
    height = h;
    depth = d;
  }
}
  
public class Main {
  public static void main(String args[]) {
    LegoBlock myLegoBlock1 = new LegoBlock();
    LegoBlock myLegoBlock2 = new LegoBlock();
    double vol;

    // initialize each box
    myLegoBlock1.setDim(10, 20, 15);
    myLegoBlock2.setDim(3, 6, 9);    

    // get volume of first lego 
    vol = myLegoBlock1.volume();
    System.out.println("Volume is " + vol);

    // get volume of second lego
    vol = myLegoBlock2.volume();
    System.out.println("Volume is " + vol);
  }
}

Create Method with Objects parameter in Java

We can pass objects to methods.

For example, consider the following short program: 

// Objects may be passed to methods.
class Test {/*  www.  j a  va  2 s  . c om*/
  int a, b;

  Test(int i, int j) {
    a = i;
    b = j;
  }

  // return true if o is equal to the invoking object
  boolean equalTo(Test o) {
    if(o.a == a && o.b == b) return true;
    else return false;
  }
}

public class Main {
  public static void main(String args[]) {
    Test ob1 = new Test(100, 22);
    Test ob2 = new Test(100, 22);
    Test ob3 = new Test(-1, -1);
    
    System.out.println("ob1 == ob2: " + ob1.equalTo(ob2));

    System.out.println("ob1 == ob3: " + ob1.equalTo(ob3));
  }
}

The equalTo() method compares two objects for equality.




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