java数组的怎删改查

import java.util.List;
import java.util.ArrayList;
import java.util.Set;
import java.util.HashSet;
public class lzwCode {  

    public static void main(String [] args) {
        testA();
        System.out.println("===========================");
        testB();
        System.out.println("===========================");
        testC();
    }  

    //去掉数组中重复的值
    public static void testA() {
        String [] str = {"Java", "C++", "Php", "C#", "Python", "C++", "Java"};
        for (String elementA:str ) {
            System.out.print(elementA + " ");
        }
        List<String> list = new ArrayList<String>();
        for (int i=0; i<str.length; i++) {
            if(!list.contains(str[i])) {
                list.add(str[i]);
            }
        }
        /*
        Set<String> set = new HashSet<String>();
        for (int i=0; i<str.length; i++) {
            set.add(str[i]);
        }
        String[] newStr =  set.toArray(new String[1]);
        */
        System.out.println();
        String[] newStr =  list.toArray(new String[1]); //返回一个包含所有对象的指定类型的数组
        for (String elementB:newStr ) {
            System.out.print(elementB + " ");
        }
        System.out.println();
    }  

    //删除数组中其中一个元素
    public static void testB() {
        String [] str = {"Java", "C++", "Php", "C#", "Python"};
        for (String elementA:str ) {
            System.out.print(elementA + " ");
        }
        //删除php
        List<String> list = new ArrayList<String>();
        for (int i=0; i<str.length; i++) {
            list.add(str[i]);
        }
        list.remove(2); //list.remove("Php")
        System.out.println();
        String[] newStr =  list.toArray(new String[1]); //返回一个包含所有对象的指定类型的数组
        for (String elementB:newStr ) {
            System.out.print(elementB + " ");
        }
        System.out.println();
    }  

    //在数组中增加一个元素
    public static void testC() {
        String [] str = {"Java", "C++", "Php", "C#", "Python"};
        for (String elementA:str ) {
            System.out.print(elementA + " ");
        }
        //增加ruby
        List<String> list = new ArrayList<String>();
        for (int i=0; i<str.length; i++) {
            list.add(str[i]);
        }
        list.add(2, "ruby"); //list.add("ruby")
        System.out.println();
        String[] newStr =  list.toArray(new String[1]); //返回一个包含所有对象的指定类型的数组
        for (String elementB:newStr ) {
            System.out.print(elementB + " ");
        }
        System.out.println();
    }
}