Java知识点归纳总结

class Singleton
{
        private static Singleton instance;
        private Singleton(){}
        public static Singleton getInstance()
        {
                if(instance == null)
                {
                        instance = new Singleton();
                }
                return instance;
        }

        public static void main(String[] args)
        {
                Singleton s1 = Singleton.getInstance();
                Singleton s2 = Singleton.getInstance();
                System.out.println(s1 == s2);
        }
}

class CacheImmutale
{
 private static int MAX_SIZE = 10;
 private static CacheImmutale[] cache = new CacheImmutale[MAX_SIZE];
 private static int pos = 0;
 private final String name;
 private CacheImmutale(String name)
 {
  this. name = name;
 }
 public String getName()
 {
  return name;
 }
 public static CacheImmutale valueOf(String name)
 {
  for(int i = 0; i < MAX_SIZE; ++i)
  {
   if(cache[i] != null && cache[i].getName().equals(name))
    return cache[i];
  }
  if(pos == MAX_SIZE)
  {
   cache[0] = new CacheImmutale(name);
   pos = 1;
  }
  else
  {
   cache[pos++] = new CacheImmutale(name);
  }
  return cache[pos -1];
 }

 public boolean equals(Object obj)
 {
  if(this == obj)
   return true;
  if(obj != null && obj.getClass() == CacheImmutale.class)
  {
   CacheImmutale ci = (CacheImmutale)obj;
   return name.equals(ci.getName());
  }
  return false;
 }
 public int hashCode()
 {
  return name.hashCode();
 }
}

public class CacheImmuteTest
{
 public static void main(String[] args)
 {
  CacheImmutale c1 = CacheImmutale.valueOf("Hello");
  CacheImmutale c2 = CacheImmutale.valueOf("Hello");
  System.out.println(c1 == c2);
 }
}

import java.util.*;

public class DiscernVariable 
{
 private String prop = "外部类的实例变量";
 private class InClass
 {
  private String prop = "内部类的实例变量";
  public void info()
  {
   String prop = "局部变量";
   System.out.println("外部类的field值：" + DiscernVariable.this.prop);
   System.out.println("内部类的field值：" + this.prop);
   System.out.println("局部变量的值：" + prop);
  }
 }
 public void test()
 {
  InClass in = new InClass();
  in.info();
 }
 public static void main(String[] args)
 {
  new DiscernVariable().test();
 }
}

import java.util.*;

class Out
{
 class In
 {
  public In()
  {
   System.out.println("非静态内部类构造器");
  }
 }
}

public class CreatInnerInstance
{
 public static void main(String[] args)
 {
  Out.In in = new Out().new In();
  /*
  以上的代码可分开写为：
  Out.In in;
  Out out = new Out();
  in = out.new In();
  */
 }
}

class SubClass extends Out.In
{
 //显示定义SubClass的构造器
 public SubClass(Out out)
 {
  //通过转入的Out对象显示调用In的构造器
  out.super();
 }
}

import java.util.*;

class StaticOut
{
 static class StaticIn
 {
  public StaticIn()
  {
   System.out.println("静态内部类构造器");
  }
 }
}

public class CreatStaticInnerInstance
{
 public static void main(String[] args)
 {
  StaticOut.StaticIn in = new StaticOut.StaticIn();
  /*
  以上的代码可分开写为：
  StaticOut.StaticIn in;
  in = new StaticOut.StaticIn();
  */
 }
}

class SubClass extends StaticOut.StaticIn
{
 //无须创建内部类实例
}