day15/GenericDemo4.java

本文介绍了Java中泛型的概念,特别是如何在类和方法级别使用泛型。重点讲解了静态泛型方法的特点及其限制条件,包括为何不能访问类级别的泛型以及如何在静态方法中定义泛型。
/*
静态泛型方法:

特殊之外:
静态方法不可以访问类上定义的泛型。
如果静态方法操作的引用数据类型不确定,可以将泛型定义在方法上。
*/

class Demo<T>
{
	public void show(T t)
	{
		System.out.println("show:"+t);
	}
	public <Q> void print(Q q)//泛型类里面再定义泛型方法。泛型方法可以不用和泛型类保持一致。
	{
		System.out.println("print:"+q);
	}

	public static <W> void method(W w)//静态方法存在时,对象还不存在(可以用类名调用),所以静态方法必须是泛型方法
	{
		System.out.println("method:"+w);
	}
}
class GenericDemo4
{
	public static void main(String[] args) 
	{
		Demo<String> d = new Demo<String>();
		d.show("haha");
		//d.show(4);//有此句就会编译失败。泛型类。

		d.print("hello");//泛型方法
		d.print(4);

		Demo.method("hi");
		//d.method(4);
	}
}

发生了这样的错误org.junit.platform.commons.PreconditionViolationException: Classpath resource [/com/main/nextDay.csv] does not exist at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:215) at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1709) at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:570) at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:560) at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151) at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174) at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:265) at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:636) at java.base/java.util.stream.ReferencePipeline$7$1FlatMap.accept(ReferencePipeline.java:294) at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:215) at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:215) at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:215) at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1709) at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:570) at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:560) at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151) at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174) at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:265) at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:636) at java.base/java.util.stream.ReferencePipeline$7$1FlatMap.accept(ReferencePipeline.java:294) at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1709) at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:570) at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:560) at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151) at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174) at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:265) at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:636) at java.base/java.util.ArrayList.forEach(ArrayList.java:1597) at java.base/java.util.ArrayList.forEach(ArrayList.java:1597) Suppressed: org.junit.platform.commons.PreconditionViolationException: Configuration error: You must configure at least one set of arguments for this @ParameterizedTest at java.base/java.util.stream.AbstractPipeline.close(AbstractPipeline.java:355) at java.base/java.util.stream.ReferencePipeline$7$1FlatMap.accept(ReferencePipeline.java:289) ... 9 more
03-24
评论
添加红包

请填写红包祝福语或标题

红包个数最小为10个

红包金额最低5元

当前余额3.43前往充值 >
需支付:10.00
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明:

1.余额是钱包充值的虚拟货币,按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载,可以购买VIP、付费专栏及课程。

余额充值