自定义ArrayList(三)-增加set()、get()方法

自定义ArrayList(三)

此次增加增加set()、get()方法来操作变量，保证其严密性。

public E get(int index) {
	// TODO Auto-generated method stub
	checkRange(index);
	return (E)elementData[index];
}

public void set(E element,int index) {
	checkRange(index);
	elementData[index] = element;
}

增加索引检查， 索引合法判断[0,size]，10   0-9完善索引。

public void checkRange(int index) {
    if (index < 0 || index > size-1) {
            throw new RuntimeException("索引不合法！"+index);   
		}
	}

对capacity进行检查，使代码更加严密

public SetArrayList3 (int capacity) {
	// 检查capacity
	if (capacity < 0) {
		throw new RuntimeException("容器容量不能为负数");
	}else if (capacity == 0) {
		elementData = new Object[DEFALT_CAPACITY];
	}else {
		elementData = new Object[capacity];
	} 
}

代码整合：

package cn.xiaomu_mycollection;
/*
 * @author 小沐
 * @param <E>
 */
public class SetArrayList3<E> {
	private Object[] elementData;  // 数组
	private int size;              // 长度
	private static final int DEFALT_CAPACITY=10;    //默认数组长度
	
	public  SetArrayList3() {
		elementData = new Object[DEFALT_CAPACITY]; 
	}
	
	public SetArrayList3 (int capacity) {
		// 检查capacity
		if (capacity < 0) {
			throw new RuntimeException("容器容量不能为负数");
		}else if (capacity == 0) {
			elementData = new Object[DEFALT_CAPACITY];
		}else {
			elementData = new Object[capacity];
		}	 
	}
	
	public void add(E element) {	
		if (size == elementData.length) {
		Object[] newobjects = new Object[/* elementData.length*2 */elementData.length+ (elementData.length << 1);   
		
	System.arraycopy(elementData, 0, newobjects, 0, elementData.length);
		elementData = newobjects;
		}
		elementData[size++] = element;
	}
	
	public E get(int index) {
		// TODO Auto-generated method stub
		checkRange(index);
		return (E)elementData[index];
	}
	
	public void set(E element,int index) {
		checkRange(index);
		elementData[index] = element;
	}
	
	public void checkRange(int index) {
		
		if (index < 0 || index > size-1) {
			throw new RuntimeException("索引不合法！"+index);   // 抛出异常
		}
	}
	@Override
	public String toString() {  // 重写toString方法
		// TODO Auto-generated method stub
		StringBuilder sBuilder = new StringBuilder();
		//a,b,c
		sBuilder.append("[");
			 
		sBuilder.setCharAt(sBuilder.length()-1, ']');
		
		return sBuilder.toString();
	}
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		SetArrayList3 s1 = new SetArrayList3(20);
		for (int i = 0; i < 20; i++) {
			s1.add("#"+i);   			
		}
		s1.set("worder", 1);
		System.out.println(s1);
		System.out.println(s1.get(10));	
	}
}