Java代码质量的优化点

1.switch 和 if/else 的性能比较

　　直接上代码：

　　　　

public class SwitchCompIfElseTest {

    @Test
    public void switchCompIfElseTest() {
        long startTimeSwitch = System.nanoTime();
        for (int i = 0; i < 1; i++) {
            switchTest(i);
        }
        long timeSwitch = System.currentTimeMillis() - startTimeSwitch;
        System.out.println("timeSwitch=" + timeSwitch);

        long startTimeIfElse = System.currentTimeMillis();
        for (int i = 0; i < 1; i++) {
            ifElseTest(i);
        }
        long timeIfElse = System.nanoTime() - startTimeIfElse;
        System.out.println("timeIfElse=" + timeIfElse);
    }

    private void switchTest(int i) {
        switch (i) {
            case 0:
                System.out.println("i=" + i);
                break;
            case 1:
                System.out.println("i=" + i);
                break;
            case 2:
                System.out.println("i=" + i);
                break;
            case 3:
                System.out.println("i=" + i);
                break;
            case 4:
                System.out.println("i=" + i);
                break;
            case 5:
                System.out.println("i=" + i);
                break;
            case 6:
                System.out.println("i=" + i);
                break;
            case 7:
                System.out.println("i=" + i);
                break;
            case 8:
                System.out.println("i=" + i);
                break;
            case 9:
                System.out.println("i=" + i);
                break;
            default:
                System.out.println("i=" + i);
                break;
        }
    }

    private void ifElseTest(int i) {
        if (i == 0) {
            System.out.println("i=" + i);
        } else if (i == 1) {
            System.out.println("i=" + i);
        } else if (i == 2) {
            System.out.println("i=" + i);
        } else if (i == 3) {
            System.out.println("i=" + i);
        } else if (i == 4) {
            System.out.println("i=" + i);
        } else if (i == 5) {
            System.out.println("i=" + i);
        } else if (i == 6) {
            System.out.println("i=" + i);
        } else if (i == 7) {
            System.out.println("i=" + i);
        } else if (i == 8) {
            System.out.println("i=" + i);
        } else if (i == 9) {
            System.out.println("i=" + i);
        } else {
            System.out.println("i=" + i);
        }
    }

}

　　

　　测试结果：