java tips

Tips是平时随手乱记下的，的确很实用，但是也特别杂乱。有些东西是小技巧，有些知识点扩展开可能写许多。如果有疑问，直接找我。

find class in jars

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find . -name *.jar -maxdepth 4 -exec grep -Hlsi org.apache.util.CacheLRU.class {} ;

The type parameter V is hiding the type V

A-E, P, V

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@SuppressWarnings ("hiding")

Manage Java version on macos

https://stackoverflow.com/questions/21964709/how-to-set-or-change-the-default-java-jdk-version-on-os-x

• Find Installed Javas

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  /usr/libexec/java_home -V
  Matching Java Virtual Machines (5):
    10.0.1, x86_64:   "Java SE 10.0.1"    /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
    1.8.0_172, x86_64:    "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_172.jdk/Contents/Home
    1.8.0_131, x86_64:    "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_131.jdk/Contents/Home
    1.8.0_65, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_65.jdk/Contents/Home
    1.7.0_80, x86_64: "Java SE 7" /Library/Java/JavaVirtualMachines/jdk1.7.0_80.jdk/Contents/Home
  
  
  
  
  
  

• switch java by JAVA_HOME variant

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  export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_172.jdk/Contents/Home
  
  
  
  
  
  

compiler识别exception

以下代码在jdk6上编译失败，7及以上ok，原因是新的编译器能识别这个实际上的异常。

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public static void main(String[] args) {

    try {
        throw new RuntimeException();
    } catch (Exception e) {
        throw e;
    }
}