Java object comparer and cloning

I. Comparator comparable and comparator The previous blog introduced the Tool class arrays tool class. We can call the Arrays.sort () function on an array of basic types to sort the array. Sorting operations are often used in daily development. Then can the string class and custom classes be sorted using Arrays.sort (). Let's try it as follows: Java code publicclassmystring { Publicstaticvoidmain (string[] args) { String []a={"Morning", "noon", "Afternoon", "evening", "Evening"}; Person[] b={Newperson ("Small white", ","), Newperson ("Little Black", 19), Newperson ("Little Red", Newperson), ("Little Violet", 20)}; Arrays.sort (a); for (inti=0;i<a.length;i++) System.out.print (A[i]); System.out.print ("\ r \ n"); Arrays.sort (b); for (inti=0;i<b.length;i++) System.out.println (B[i]); } } Custom Classes Classperson { Publicstring name; Publicintage; Publicperson (String name,intage) { This.name=name; This.age=age; } } Program Run Result: We find that string can call the Arrays.sort () function, and we customize the person class to make an error, looking at the wrong keyword comparable Open String Source By introducing the comparator comparable, we use the comparable interface below to implement the person using Arrays.sort () to sort the ascending order by age. The comparable interface is able to sort the objects that implement its classes, using the CompareTo function primarily for sorting. The CompareTo function returns the int type, which returns -1,0,1, which corresponds to less than, equal to, greater than. Change the code to: Java code publicclassmystring { Publicstaticvoidmain (string[] args) { String []a={"Morning", "noon", "Afternoon", "evening", "Evening"}; Person[] b={Newperson ("Small white", ","), Newperson ("Little Black", 19), Newperson ("Little Red", Newperson), ("Little Violet", 20)}; Arrays.sort (a); for (inti=0;i<a.length;i++) System.out.print (A[i]); System.out.print ("\ r \ n"); Arrays.sort (b); for (inti=0;i<b.length;i++) System.out.println (B[i]); } } Custom Classes Classperson implementscomparable<person>{ Publicstring name; Publicintage; Publicperson (String name,intage) { This.name=name; This.age=age; } Comparator comparison function /** * Returns 1 if the current object is less than the comparison object * Returns 0 if the current object equals the comparison object * Returns 1 if the current object is greater than the comparison object */ @Override Publicintcompareto (person O) { Object is empty, throws a null pointer exception if (o==null) Thrownewnullpointerexception (); if (this.age<o.age) return-1; if (this.age>o.age) RETURN1; Return0; } Overriding the ToString Method @Override Publicstring toString () { return "person [name=" + name + ", age=" + Age + "]"; } } Operation Result: To implement the comparer comparable interface for the custom person, you can call Arrays.sort () to sort. There is another way to implement the comparator interface. Java code publicclassmystring { Publicstaticvoidmain (string[] args) { String []a={"Morning", "noon", "Afternoon", "evening", "Evening"}; Person[] b={Newperson ("Small white", ","), Newperson ("Little Black", 19), Newperson ("Little Red", Newperson), ("Little Violet", 20)}; Arrays.sort (a); for (inti=0;i<a.length;i++) System.out.print (A[i]); System.out.print ("\ r \ n"); Arrays.sort (B,newpersoncomparator ()); for (inti=0;i<b.length;i++) System.out.println (B[i]); } } Custom Classes Classperson { Publicstring name; Publicintage; Publicperson (String name,intage) { This.name=name; This.age=age; } @Override Publicstring toString () { return "person [name=" + name + ", age=" + Age + "]"; } } Classpersoncomparator implementscomparator<person>{ Comparator comparison function /** * Returns 1 if the current object is less than the comparison object * Returns 0 if the current object equals the comparison object * Returns 1 if the current object is greater than the comparison object */ @Override Publicintcompare (person O1, person O2) { Object is empty, throws a null pointer exception if (o1==null| | O2==null) Thrownewnullpointerexception (); if (o1.age<o2.age) return-1; if (o1.age>o2.age) RETURN1; Return0; } } Two. Cloning clone of an object Copies a copy of an object, called the object's cloning technique. Cloning an object is a two-step move. 1. Implement cloneable Tag interface Cloneable is a markup interface that does not have any methods defined by this interface. Just as a token to the virtual machine. 2. Overriding the Clone method of object Java code Custom class person implementation cloneable interface Classperson implementscloneable { Publicstring name; Publicintage; Publicperson (String name,intage) { This.name=name; This.age=age; } Overriding the Clone method of object @Override Protectedobject Clone () throwsclonenotsupportedexception { Returnsuper.clone (); } } Cloned calls: Java code Publicstaticvoidmain (string[] args) { Person Temp=newperson ("Wang Nima", 18); try{ Person ok= (person) temp.clone ();//Convert the object class to person, System.out.println (ok.name);//Output Wang Nima } catch (Clonenotsupportedexception e) { E.printstacktrace (); } } This can be done to clone an object, when we want to create a series of similar objects, you can consider the use of cloning technology can get better performance, than you create better.

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Java object comparer and cloning