This is a question about String compare.The result is different if generate string with different way--one is using keyword "new",another isn't.Please help me answer:Why did this happen?What difference between these two way?Where does the string object store?Stack or heap?on the other hand,please correct my language error.
This is my program:
public class CompareString
{public static void main(String[] args)
{String string1=new String("good");
String string2=new String("good");//first way,generate string with "new",answer is "false".
//String string1="good";
//String string2="good";//second way,generate string without "new",answer is "true".
System.out.println("string1 equal string2 is:"+(string1==string2));
}
}
| freedomRen (2004-01-26 18:14:00) |
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首先可以知道的是==操作是引用比較
String string1=new String("good");
String string2=new String("good");
new 操作創建了新的字符串對象並初始化爲good,string1,string2分別引用了各自的實例
因此引用比較結果爲false
String string1="good";
String string2="good";
Java中的字符串常量存在constant poll中標記爲CONSTANT_String，
爲了解析標記爲CONSTANT_String的常數池表項，當JVM載入.class文件，處理字符串變量時要進行常數池解析constant poll resolution的操作。如果表示相同序列的Unicode字符的另一個常數池已經被解析，那麼解析的結果是對已有的那個常量池表項的String實例的引用，也就是說此時string1，string2是引用同一個實例
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| wen00000000 (2004-01-27 1:17:00) |
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System.out.println("string1 equal string2 is:"+(string1.equals(string2)));
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| sunruijia (2004-02-11 15:09:46) |
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字符串比較應該用String的equals方法，用== 只是比較兩個引用string1和string2是否指向同一個對象
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