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java封裝類型與基礎(chǔ)類型對比示例分析

更新時間：2023年11月22日 10:17:26 作者：求平安

這篇文章主要為大家介紹了java封裝類型與基礎(chǔ)類型對比示例分析,有需要的朋友可以借鑒參考下,希望能夠有所幫助,祝大家多多進(jìn)步,早日升職加薪

封裝類型以Long為例，基礎(chǔ)類型以long為例

1 比較equals與==

@Test
public void testEquals() {
    Long l1 = 10000L;
    long l2 = 10000l;
    Long l3 = 10000l;
    // 封裝類型與基礎(chǔ)類型==比較的時候，封裝類型會自動轉(zhuǎn)成基本類型做比較
    System.out.println(l1 == l2); // true
    System.out.println(l1 == l3); // false
    System.out.println(l1.longValue() == l3.longValue()); // true
}

總結(jié)1：如果使用==號比較，需要把1側(cè)的類型轉(zhuǎn)成基礎(chǔ)類型

2 速度equals與==哪個更快呢？

@Test
public void testFast() {
    // string的equals和long的equals，哪個更快
    int N = 1000000;
    long[] l1 = new long[N];
    long[] l2 = new long[N];
    Long[] data1 = new Long[N];
    Long[] data2 = new Long[N];
    String[] str1 = new String[N];
    String[] str2 = new String[N];
    long j = 0;
    for (int i = 0; i < N; i++) {
        data1[i] = j;
        data2[i] = j;
        str1[i] = String.valueOf(j);
        str2[i] = String.valueOf(j++);
    }
    compareL(l1, l2, N); // 10
    compareLong1(data1, data2, N); // 100
    compareLong(data1, data2, N); // 600
    // 總結(jié)：Long1.longValue()==Long2.longValue() 比 Long1.equals(Long2) 更快
    compareStr(str1, str2, N); // 1000
}
public void compareL(long[] data1, long[] data2, int N) {
    long startL = System.currentTimeMillis();
    for (int i = 0; i < 100; i++) {
        for (int j = 0; j < N; j++) {
            if (data1[j] == (data2[j])) {
            }
        }
    }
    long endL = System.currentTimeMillis();
    System.out.println("compareL tasks times :" + (endL - startL));
}
public void compareLong(Long[] data1, Long[] data2, int N) {
    long startL = System.currentTimeMillis();
    for (int i = 0; i < 100; i++) {
        for (int j = 0; j < N; j++) {
            if (data1[j].equals(data2[j])) {
            }
        }
    }
    long endL = System.currentTimeMillis();
    System.out.println("compareLong tasks times :" + (endL - startL));
}
public void compareLong1(Long[] data1, Long[] data2, int N) {
    long startL = System.currentTimeMillis();
    for (int i = 0; i < 100; i++) {
        for (int j = 0; j < N; j++) {
            if (data1[j].longValue() == data2[j].longValue()) {
            }
        }
    }
    long endL = System.currentTimeMillis();
    System.out.println("compareLong tasks times :" + (endL - startL));
}
public void compareStr(String[] data1, String[] data2, int N) {
    long startL = System.currentTimeMillis();
    for (int i = 0; i < 100; i++) {
        for (int j = 0; j < N; j++) {
            if (data1[j].equals(data2[j])) {
            }
        }
    }
    long endL = System.currentTimeMillis();
    System.out.println("compareStr tasks times :" + (endL - startL));
}