浅谈Processing中的 println() 打印输出函数[String]

简单看一下Processing中的打印输出函数println()相关用法。

部分源码学习

  /**
   * ( begin auto-generated from println.xml )
   *
   * Writes to the text area of the Processing environment's console. This is
   * often helpful for looking at the data a program is producing. Each call
   * to this function creates a new line of output. Individual elements can
   * be separated with quotes ("") and joined with the string concatenation
   * operator (+). See <b>print()</b> for more about what to expect in the output.
   * <br/><br/> <b>println()</b> on an array (by itself) will write the
   * contents of the array to the console. This is often helpful for looking
   * at the data a program is producing. A new line is put between each
   * element of the array. This function can only print one dimensional
   * arrays. For arrays with higher dimensions, the result will be closer to
   * that of <b>print()</b>.
   *
   * ( end auto-generated )
 * @webref output:text_area
 * @usage IDE
 * @see PApplet#print(byte)
 * @see PApplet#printArray(Object)
 */
  static public void println() {
    System.out.println();
  }

  /**
   * @param variables list of data, separated by commas
   */
  static public void println(Object... variables) {
//    System.out.println("got " + variables.length + " variables");
    print(variables);
    println();
  }

学习成效

很明显，按照源码编写，就是调了System.out.println();，而且还拓展了形参类型Object... variables,如下面的用法：

int a = 9;
String b = "what";
float c = 54.3f;
println(a,b,c);

输出：

9 what 54.3

也就是说在括号里，你可以陆续把需要打印的值加进去，用“，”分割，它自动以一个空格字符分割并连续输出。

当然基本写法应该是这样子(等价)：

println(a+" " + b + " " +c);

还有一种占位符用法[1]：

System.out.printf("%d %s %f",a,b,c);

当然还可以用String类中的方法转换：

String str = String.format("%d %s %f",a,b,c);
println(str);

还可以使用MessageFormat相关方法[2]：

import java.text.MessageFormat;

String message = MessageFormat.format("{0} {1} {2}", a,b,c);
println(message);

当然如果需求奇异苛刻，还可以自定义算法或者使用模板引擎，所谓“字符串模板”,请看参考文章[2]。

尾声

java语言确实是老了，不如新生代灵活，比如Kotlin,它自带的字符串模板就很好用，如下：

val a = 9
val b = "what"
val c = 54.3f
println("$a $b $c")

不过既然java依旧是编程界的大佬，它的规则是经历了千锤百炼的，好好学，必有价值！~

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参考：

[1] https://www.cnblogs.com/happyday56/p/3996498.html ------ java占位符使用

[2] https://www.cnblogs.com/softidea/p/9140204.html ------ java 替换字符串模板(模板渲染)