Java Generic Method

In this chapter you will learn:

  1. What is generic method
  2. Example for generic method
  3. Example - copyList() generic method

Description

It is possible to create a generic method that is enclosed within a non-generic class.

Example


public class Main {
  static <T, V extends T> boolean isIn(T x, V[] y) {
    for (int i = 0; i < y.length; i++) {
      if (x.equals(y[i])) {
        return true;
      }//www.ja  v a 2  s .com
    }
    return false;
  }

  public static void main(String args[]) {
    Integer nums[] = { 1, 2, 3, 4, 5 };
    if (isIn(2, nums)){
      System.out.println("2 is in nums");
    }
    String strs[] = { "one", "two", "three", "four", "five" };
    if (isIn("two", strs)){
      System.out.println("two is in strs");
    }
  }
}

The code above generates the following result.

Example 2

The following code declares a copyList() generic method.


//  w  ww.  ja v a  2  s .c  o m
import java.util.ArrayList;
import java.util.List;

public class Main {
  public static void main(String[] args) {
    List<String> ls = new ArrayList<String>();
    ls.add("A");
    ls.add("B");
    ls.add("C");
    List<String> lsCopy = new ArrayList<String>();
    copyList(ls, lsCopy);
    List<Integer> lc = new ArrayList<Integer>();
    lc.add(0);
    lc.add(5);
    List<Integer> lcCopy = new ArrayList<Integer>();
    copyList(lc, lcCopy);
  }

  static <T> void copyList(List<T> src, List<T> dest) {
    for (int i = 0; i < src.size(); i++)
      dest.add(src.get(i));
  }
}

Next chapter...

What you will learn in the next chapter:

  1. Example - How to create a generic constructor
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      Java Generics
Java Generic Type
Java Generic Bounded Types
Java Generic Method
Java Generic Constructors
Java Generic Parameter Wildcard
Java Generic interface
Java Raw Types and Legacy Code
Java Generic Class Hierarchies
Java generic types cast
Java Generic Restrictions