Some chunks of Java code

ArrayAlgo.java

import java.util.Random;

public class Main
{
  private static void doThing(int[] param, int x, int y)
  {
    if (x >= y)
      return;
    
    int i = x;
    int j = y-1;
    int p = param[y];
    while(i < j)
    {
      while (param[i] >= p && i < y)
        i++;
      
      while (param[j] <= p && j > x)
        j--;
        
      if (i < j)
      {
        int t = param[i];
        param[i] = param[j];
        param[j] = t;
      }
    }
    
    if (param[i] < p)
    {
        int t = param[i];
        param[i] = param[y];
        param[y] = t;
    }
    
    doThing(param,x,i-1);
    doThing(param,i+1,y);
  }
  
  public static void main(String[] args)
  {
    Random rng = new Random(); //Random number generator
    int[] xs = new int[100];
    for (int i = 0; i < 100; ++i)
      xs[i] = rng.nextInt(100); //nextInt(x) generates random number between 0 and x-1 (inclusive)
      
    doThing(xs,0,99);
    System.out.print("[");
    for (int i = 0; i < 100; ++i)
    {
      System.out.print(xs[i]);
      if (i < 99)
        System.out.print(", ");
    }
    System.out.print("]");
  }
}

Conditionals1.java

public class Main
{
  private static int foo(int x)
  {
    if (x != 1 || x != 2)
      x = 3;
    
    return x;
  }
  public static void main(String[] args)
  {
    for (int i = 0; i < 3; ++i)
      System.out.println(foo(i));
  }
}

Conditionals2.java

public class Main
{
  private static int foo(int x)
  {
    if (x > x == x < x)
      x = -x;
    
    return x;
  }
  public static void Main(String[] args)
  {
    for (int i = 0; i < 3; ++i)
      System.out.println(foo(i));
  }
}

Inheritance2.java

class A
{
  public void foo(float f)
  {
    System.out.println("A");
  }
}

class B extends A
{
  public void foo(int i)
  {
    System.out.println("B");
  }
}

class C extends B
{
  public void foo(int i)
  {
    System.out.println("C");
  }
}

public class Main
{
  public static void main(String[] args)
  {
    A a = new A();
    a.foo(1);
    B b = new B();
    b.foo(1);
    a = b;
    a.foo(1);
    b.foo(1);
    b = new C();
    a.foo(1);
    b.foo(1);
  }
}

Inheritance3.java

class A
{
  public void foo(int f)
  {
    System.out.println("A");
  }
}

class B extends A
{
  public void foo(float i)
  {
    System.out.println("B");
  }
}

class C extends B
{
  public void foo(int i)
  {
    System.out.println("C");
  }
}

public class Main
{
  public static void main(String[] args)
  {
    A a = new A();
    a.foo(1);
    B b = new B();
    b.foo(1);
    a = b;
    a.foo(1);
    b.foo(1);
    b = new C();
    a.foo(1);
    b.foo(1);
  }
}

Interitance1.java

class A
{
  public void foo()
  {
    System.out.println("A");
  }
}

class B extends A
{
  public void foo()
  {
    System.out.println("B");
  }
}

class C extends B
{
  public void foo()
  {
    System.out.println("C");
  }
}

public class Main
{
  public static void main(String[] args)
  {
    A a = new A();
    a.foo();
    B b = new B();
    b.foo();
    a = b;
    a.foo();
    b.foo();
    b = new C();
    a.foo();
    b.foo();
  }
}

Loops1.java

public class Main
{
  public static void main(String[] args)
  {
    boolean c = true;
    int i = 0;
    while(c)
    {
      if (i > 5)
        break;
      
      while (i < 3)
      {
        ++i;
        System.out.println(i);
      }
      System.out.println(i);
    }
    System.out.println("Over.");
  }
}

Recursion1.java

public class Main
{
  private static int func(int x)
  {
    if (x < 1)
      return 1;
    
    return x * f(x-1);
  }
  
  public static void main(String[] args)
  {
    for (int i = -1; i < 5; ++i)
      System.out.println(func(i));
  }
}

Recursion2.java

public class Main
{
  private static boolean funcA(int x)
  {
    if (x == 0)
      return true;
    else
      return funcB(x - 1);
  }
  private static boolean funcB(int x)
  {
    if (x == 0)
      return false;
    else
      return funcA(x - 1);
  }
  
  public static void main(String[] args)
  {
      System.out.println(funcA(2) ? "true" : "false");
      System.out.println(funcA(0) ? "true" : "false");
      System.out.println(funcA(1) ? "true" : "false");
      System.out.println(funcA(5) ? "true" : "false");
      System.out.println(funcA(128) ? "true" : "false");
      System.out.println(funcA(2015) ? "true" : "false");
  }
}

Recursion3.java

public class Main
{
  private static int a(int x, int y)
  {
    if (x == 0)
      return y+1;
    if (y == 0)
      return a(x-1,1);
    return a(x-1,a(x,y-1))
  }
  
  public static void main(String[] args)
  {
    System.out.println(a(2,2));
  }
}