Java实现顺序表的增删查改功能

public class MyArraylist1 {

     public int [] elem; //存储数据的有效个数

     public int usedata; //有效数据的个数

     //构造方法

     public MyArraylist1() {

         this .elem = new int [ 10 ];

     }

public void add( int pos, int data) //添加元素

  public int search( int tofind) //找一个元素返回下标

  public void remove( int toRemove) //删除第一次出现的关键字toRemove

  public void setPos( int pos, int value) //给 pos 位置的元素设为 value

  public void display() //打印元素

/ / 添加元素

     public void add( int pos, int data) {

         / / 1. 判断顺序表是否为满

         if (this.elem.length = = this.usedata) {

             System.out.println( "满了，扩充" );

             this.elem = Arrays.copyOf(this.elem,this.elem.length * 2 );

         }

         / / 2 ，pos位置有效性

         if (pos< 0 || pos>this.usedata) {

             System.out.println( "不合法" );

             return ;

         }

         / / 3 ,插入

         for ( int i = this.usedata - 1 ; i> = pos  ; i - - ) {

             this.elem[i + 1 ] = this.elem[i];

         }

         this.elem[pos] = data;

         usedata + + ;

     }

/ / 查找一个元素返回下标

     public int search( int tofind) {

         / / 1. 判断顺序表是否为空

         if (this.usedata = = 0 ) {

             throw new RuntimeException( "顺序表为空" );

         }

         / / 2. 查找

         for ( int i = 0 ; i < this.usedata ; i + + ) {

             if (this.usedata = = tofind) {

                 return i;

             }

         }

         return - 1 ;

//删除第一次出现的关键字toRemove

    public void remove( int toRemove) {

        //1.判断是否含有这个关键字

        int index = search(toRemove);

        if (index == - 1 ) {

            System.out.println( "删除的关键字不存在" );

            return ;

        }

        //2.删除

        //主要理解i< this.usedsize-1，画图易懂，比如有1,2,3三个数，要删除0号下标，i=0;i<2;i++,从后向前覆盖两次。

        for ( int i = index; i < this .usedata- 1 ; i++) {

            this .elem[i] = this .elem[i+ 1 ];

        }

        usedata--;

    }

// 给 pos 位置的元素设为 value

     public void setPos( int pos, int value) {

         //1.判断顺序表是否为空

         if ( this .usedata == 0 ) {

             throw new RuntimeException( "顺序表为空" );

         }

         //2.判断pos位置有效性

         if (pos< 0 || pos>= this .usedata) {

             return ;

         }

         //3.修改值为value

         this .elem[pos] =value;

     }

//打印元素

     public void display() {

         for ( int i = 0 ; i < this .usedata ; i++) {

             System.out.print( this .elem[i]+ " " );

         }

         System.out.println();

     }

public class TestList1 {

     public static void main(String[] args) {

         MyArraylist1 myArraylist1 = new MyArraylist1();

         myArraylist1.add( 0 , 1 );

         myArraylist1.add( 0 , 2 );

         myArraylist1.add( 0 , 3 );

         myArraylist1.add( 0 , 4 );

         myArraylist1.add( 0 , 5 );

         System.out.println( "========================查找===========================" );

         myArraylist1.display();

         System.out.println( "查找元素下标为：" +myArraylist1.search( 1 ));

         System.out.println( "查找元素下标为：" +myArraylist1.search( 3 ));

         System.out.println( "查找元素下标为：" +myArraylist1.search( 5 ));

         System.out.println( "========================删除===========================" );

         myArraylist1.remove( 1 );

         myArraylist1.remove( 5 );

         myArraylist1.display();

         System.out.println( "========================修改===========================" );

         myArraylist1.setPos( 0 , 2 );

         myArraylist1.setPos( 2 , 4 );

         myArraylist1.display();

     }

}