基于TDD的表达式验证

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下面是一个关于表达式验证的测试代码, 令人出乎意料的是以栈方式检验检查表达式的开销要远远超出于以查找方式对表达式进行检查.

?是否JVM对String类的所有接口作了强化？特此附上代码,期待大虾解释其原因.

测试代码:

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public class StackBasedExpressionValidator        implements ExpressionValidator {    public static final boolean POP = false;    public static final boolean PUSH = true;    public boolean validate(String expression) {        boolean state = POP;        char[] chars = expression.toCharArray();        int length = chars.length;        int k = 0;        do {            switch (chars[k]) {                case START_EL:                    if (isPushed(state))                        return false;                    state = PUSH;                    break;                case END_EL:                    if (isPopup(state))                        return false;                    state = POP;                    break;            }        } while (++k < length);        return isPopup(state);    }    private boolean isPushed(boolean state) {        return state==PUSH;    }    private boolean isPopup(boolean state) {        return state==POP;    }}