Java container-introducing the Guava class library

first, Directory

1. read-only Settings

2. Functional Programming + Modular programming

3. Constraint conditions

4. Set Operation (combination, difference set, Intersection)

second, The code implementation

1. read-only Settings

 public Static voidmain (String [] Args) {//read-only SettingsList ls=NewArrayList (); Ls.add (A); Ls.add ("b"); Ls.add (C); //class libraries that do not use guavaList <string > readlist=collections.unmodifiablelist (ls); //Readlist.add ("d"); Error//using the Guava class librarylist<string> imutablelist= immutablelist.of ("a", "b", "c"); //Imutablelist.add ("a"); Operation error
}

2. Function-type Programming

(1) function One: Find the set of Palindrome string, Palindrome also known as Mirror word, backword, refers to the string from the front or back to read the same, such as Moom

//result: Moom because Moon is moom after reverse order     public Static voidmain (string[] Args) {List<String> list = lists.newarraylist ("dog", "cat", "pig", "moom"); Collection<String> Plist=collections2.filter (list,NewPredicate<string>() {             public BooleanApply (String S) {return NewStringBuilder (s). Reverse (). toString (). equals (s);        }        }); //Anonymous inner class, create object at the same time, collections2.filter similar filter         for(Object O:plist) {System.out.println (o); }    }

(2) function Two: Date conversion

Results: 1970-01-01    1970-01-24   1970-01-02

  public Static voidmain (String [] Args) {Set<Long> timeset=Sets.newhashset (); Timeset.add (1000L); Timeset.add (2000l*1000000); Timeset.add (3000l*20000); Collection<String> translist= Collections2.transform (timeset,Newfunction<long, string>() {             publicString Apply (Long input) {return NewSimpleDateFormat ("yyyy-mm-dd"). Format (input);        }        });  for(String S:translist) {System.out.println (s); }    }

(3) function Three: Modular programming

 public Static voidmain (String [] Args) {List<String> list = lists.newarraylist ("happy", "sad", "wahaha"); //Method Onefunction<string,string>f1=Newfunction<string, string>() {             publicstring Apply (string S) {returnS.length () >5&&s.length () <20?s: "error";        }        }; //method Two: all uppercase lettersfunction<string, string> F2 =Newfunction<string, string>() {             publicstring Apply (string Input) {returnInput.touppercase ();        }        }; //Combination Methodfunction<string, string> f =functions.compose (f1, f2); Collection Resultcol=Collections2.transform (list,f);  for(Object S:resultcol) {System.out.println (s); }    }

3. Constraint conditions

  public Static voidmain (string[] Args) {Set<String> sets =Sets.newhashset (); //Create a constraintConstraint<string> Constraint =NewConstraint<string>() {@Override publicstring checkelement (string element) {//non-null ValidationPreconditions.checknotnull (element); //length limit 5-20, otherwise errorpreconditions.checkargument (element.length ()>= 5 && element.length () <= 20, element); returnelement;        }        }; Set<String> cs =Constraints.constrainedset (sets, constraint); //cs.add (null); Error java.lang.NullPointerException//cs.add ("qaz"); Error Java.lang.IllegalArgumentException:qaz}

4, intersection, set, difference set

  public Static voidmain (String [] Args) {Set<Integer> Sets=sets.newhashset (1,2,3,4,5,6); Set<Integer> Set2=sets.newhashset (3,4,5,6,7,8,9); Sets.setview<Integer> intersection =sets.intersection (sets, set2);  for(Integer In:intersection) {System.out.print ( in+"  "); } System.out.println (""); //Difference SetSets.setview<integer> intersection2=sets.difference (sets,set2);  for(Integer in:intersection2) {System.out.print ( in+"  "); } System.out.println (""); //and setSets.setview<integer> intersection3=sets.union (sets,set2);  for(Integer in:intersection3) {System.out.print ( in+"  "); }    }

Java container-introducing The Guava class library