length 和 size 辨析

最新推荐文章于 2025-09-16 17:53:38 发布

原创最新推荐文章于 2025-09-16 17:53:38 发布 · 1.4k 阅读

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本文通过几个示例对比了Java中数组与集合的长度获取方式，总结了String类型的方法length()，静态数组的length属性，动态数组（如ArrayList）的size()方法的使用区别。

import java.util.*;

public class testLengthAndSize
{
    public static void main(String[] args)
    {
        String[] a=new String[5];
        ArrayList aList=new ArrayList();
        testLengthAndSize[] test=new testLengthAndSize[5];

//        System.out.println("a.size="+a.size());                //no such method
        System.out.println("a.length="+a.length);
        System.out.println("a[0]="+a[0]);

//        System.out.println("aList.length="+aList.length);   //no such method or field
        System.out.println("aList.size="+aList.size());
//        System.out.println("aList.size="+aList.get(0));          //RuntimeExecption---IndexOutOfBoundsException

        System.out.println("test.length="+test.length);
//        System.out.println("test.size="+test.size());
        System.out.println("test[0]="+test[0]);

/** In Summary
"String" type has length() method;

"array" type does not have length() method; "static array" has length field;

"Dynamic array" type has "size()" method, but has neither length field nor length() method;
**/
        }
}