Java的String pool

Java執行時會維護一個String pool, 對於一些可以共享的字串物件, 會先在String pool中尋找, 有相同的字串內容就直接傳回, 減少記憶體的耗用.

public class test02 {
    public static void main(String args[])
    {
        String a = new String("abc");
        String b = new String("abc");
        String c = "abc";
        String d = "abc";
        String e = "def";
        String f = "abcdef";
        String g = c+e;
        String h = (c+e).intern(); 
        String i = new String("abc").intern();

        System.out.println(a == b);    // false
        System.out.println(c == d);    // true
        System.out.println(f == g);    // false
        System.out.println(f == h);    // true
    }
}