为什么java System.out.print方法有各种形式？

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我打开了java.io.PrintStream类文件。我发现有各种各样的打印方法。每个方法99%相同，但仅不包含参数类型。许多编程指南都建议在这种情况下可以使用泛型（或模板）。所以我想知道为什么java.io.Printstream不使用generic。

如果您使用

public void print(long l) {
    write(String.valueOf(l));
}

/**
 * Prints a floating-point number.  The string produced by <code>{@link
 * java.lang.String#valueOf(float)}</code> is translated into bytes
 * according to the platform's default character encoding, and these bytes
 * are written in exactly the manner of the
 * <code>{@link #write(int)}</code> method.
 *
 * @param      f   The <code>float</code> to be printed
 * @see        java.lang.Float#toString(float)
 */
public void print(float f) {
    write(String.valueOf(f));
}

/**
 * Prints a double-precision floating-point number.  The string produced by
 * <code>{@link java.lang.String#valueOf(double)}</code> is translated into
 * bytes according to the platform's default character encoding, and these
 * bytes are written in exactly the manner of the <code>{@link
 * #write(int)}</code> method.
 *
 * @param      d   The <code>double</code> to be printed
 * @see        java.lang.Double#toString(double)
 */
public void print(double d) {
    write(String.valueOf(d));
}

/**
 * Prints an array of characters.  The characters are converted into bytes
 * according to the platform's default character encoding, and these bytes
 * are written in exactly the manner of the
 * <code>{@link #write(int)}</code> method.
 *
 * @param      s   The array of chars to be printed
 *
 * @throws  NullPointerException  If <code>s</code> is <code>null</code>
 */
public void print(char s[]) {
    write(s);
}

因此，

int

值将被装箱，这意味着性能损失和不必要的内存使用

这就是您经常会发现所有primitiv数据类型的方法重载的原因

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同样正如Taschi指出的，该类在Java中比泛型更古老。

基元类型不是对象，因此不能用作泛型类型。另外，对于特定类型，某些方法确实具有特定的行为。这些方法也早于Java中泛型的存在，Java 1.0中甚至不存在自动装箱/拆箱和泛型。

public <T> void print(T value);

public void print(Integer value);