[Java set] implements a simple ArrayList and a java set arraylist.

[Java set] implements a simple ArrayList and a java set arraylist.

List interface:

public interface IMyList<E> {    E set(int index, E elem);    boolean add(E e);    boolean remove(Object o);    E remove(int index);    int indexOf(Object o);    E get(int index);    int size();    boolean isEmpty();}

ArrayList implementation:

Import java. util. arrays; public class MyArrayList <E> implements IMyList <E> {private Object [] elementData; private int size; public MyArrayList () {this (10 );} public MyArrayList (int initialCapacity) {this. elementData = new Object [initialCapacity] ;}@ Override public E set (int index, E elem) {E oldElem = elementData (index); elementData [index] = elem; return oldElem;} // check whether the space is sufficient before adding the element. If not, add @ Override public boolean add (E e) {ensureCapacity (size + 1) after resizing ); elementData [size ++] = e; return true ;}@ Override public boolean remove (Object o) {if (o = null) {for (int I = 0, len = elementData. length; I <len; I ++) if (o = elementData [I]) {fastRemove (I); return true ;}} else {for (int I = 0, len = elementData. length; I <len; I ++) if (o. equals (elementData [I]) {fastRemove (I); return true ;}} return false ;}@ Override public E remove (int index) {E oldElem = elementData (index); fastRemove (index); return oldElem;} private void fastRemove (int index) {/*** the source code is like this * int numMoved = size-index-1; * if (numMoved> 0) * System. arraycopy (elementData, index + 1, elementData, index, numMoved); **/for (int I = index + 1; I <size; I ++) {elementData [I-1] = elementData [I];} elementData [-- size] = null;} @ Override public int indexOf (Object o) {for (int I = 0, len = elementData. length; I <len; I ++) if (o = elementData [I]) return I; return-1 ;}@ Override public E get (int index) {return elementData (index) ;}@ Override public int size () {return size ;}@ Override public boolean isEmpty () {return size = 0 ;} private E elementData (int index) {return (E) elementData [index];} // if there is not enough space, you need to resize it, the size after expansion is 1.5 times that of the original private void ensureCapacity (int size) {if (size> elementData. length) {int oldCapacity = elementData. length; int newCapacity = (oldCapacity> 1) + oldCapacity; elementData = Arrays. copyOf (elementData, newCapacity );}}}

Test code:

public class Main {    public static void main(String[] args) {        IMyList<String> list = new MyArrayList<String>();        for (int i=0; i<12; i++){            list.add("s" + i);        }        list.remove("s3");        for (int i=0; i<list.size(); i++){            System.out.println(list.get(i));        }    }}

Running result:

s0s1s2s4s5s6s7s8s9s10s11

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