stringtest.java

针对String类创建对象的比较.详细比较结果请看源码文件中的说明,适合新手!

/**
*针对String类创建对象的比较
*/

/*
*常量类型对待:如果堆中有该值,则直接返回引用:
*       String a = "abcd";String b = "abcd";则a==b的值为true,a.equals(b)的值为true;
*new对象对待:新建对象:
*				String a = new String("abc");String b = new String("abc");则a==b的值为false,a.equals(b)的值为true;
*+连接符对待:
*       连接对象时候:
*       		String a = "abcd";String b = "abc";String c = "d";String d = b+c;
				那么a==d的值为false,a.equals(d)的值true;
*       直接是常量连接时候:
*           String a = "abcd";String b = "ab" + "cd";则a == b的值为true,a.equals(b)的值为true;
*/


public class StringTest
{
	public static void main(String [] args)
	{
		String a = "abcd";
		//String a = new String("abcd");
		String b = "abc";
		
		String c = "d";
		/*
		String temp = b + c;
		String d = new String(temp);
		*/
		//String d = "ab"+"cd";
		
		String d = b + c;
		
		String e = new String(b + c);
		
		
		//String f = "abcd";
		String f = new String("abcd");
		
		
		if(a == d)
		{
			System.out.println("a == d same");
		}
		else
		{
			System.out.println("a == d different");
		}
		
		if(a.equals(d))
		{
			System.out.println("a equals d");
		}
		else
		{
			System.out.println(" a don't equals d");
		}




		if(a == e)
		{
			System.out.println("a == e same");
		}
		else
		{
			System.out.println("a == e different");
		}				
		
		if(a == f)
		{
			System.out.println("a == f is true");
		}
		else 
		{
			System.out.println("a == f is false");
		}
		
	}
}